Add SNP-specific hooks to the unaccepted memory support in the boot
path (__accept_memory()) and the core kernel (accept_memory()) in order
to support booting SNP guests when unaccepted memory is present. Without
this support, SNP guests will fail to boot and/or panic() when unaccepted
memory is present in the EFI memory map.

The process of accepting memory under SNP involves invoking the hypervisor
to perform a page state change for the page to private memory and then
issuing a PVALIDATE instruction to accept the page.

Since the boot path and the core kernel paths perform similar operations,
move the pvalidate_pages() and vmgexit_psc() functions into sev-shared.c
to avoid code duplication.

Create the new header file arch/x86/boot/compressed/sev.h because adding
the function declaration to any of the existing SEV related header files
pulls in too many other header files, causing the build to fail.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
---
 arch/x86/Kconfig                         |   2 +
 arch/x86/boot/compressed/mem.c           |   3 +
 arch/x86/boot/compressed/sev.c           |  54 ++++++++++-
 arch/x86/boot/compressed/sev.h           |  23 +++++
 arch/x86/include/asm/sev.h               |   3 +
 arch/x86/include/asm/unaccepted_memory.h |   3 +
 arch/x86/kernel/sev-shared.c             | 103 +++++++++++++++++++++
 arch/x86/kernel/sev.c                    | 112 +++--------------------
 8 files changed, 204 insertions(+), 99 deletions(-)
 create mode 100644 arch/x86/boot/compressed/sev.h

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 5c72067c06d4..b9c451f75d5e 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1543,11 +1543,13 @@ config X86_MEM_ENCRYPT
 config AMD_MEM_ENCRYPT
 	bool "AMD Secure Memory Encryption (SME) support"
 	depends on X86_64 && CPU_SUP_AMD
+	depends on EFI_STUB
 	select DMA_COHERENT_POOL
 	select ARCH_USE_MEMREMAP_PROT
 	select INSTRUCTION_DECODER
 	select ARCH_HAS_CC_PLATFORM
 	select X86_MEM_ENCRYPT
+	select UNACCEPTED_MEMORY
 	help
 	  Say yes to enable support for the encryption of system memory.
 	  This requires an AMD processor that supports Secure Memory
diff --git a/arch/x86/boot/compressed/mem.c b/arch/x86/boot/compressed/mem.c
index f04b29f3572f..3c1609245f2a 100644
--- a/arch/x86/boot/compressed/mem.c
+++ b/arch/x86/boot/compressed/mem.c
@@ -3,6 +3,7 @@
 #include "error.h"
 #include "misc.h"
 #include "tdx.h"
+#include "sev.h"
 #include <asm/shared/tdx.h>
 
 /*
@@ -37,6 +38,8 @@ void arch_accept_memory(phys_addr_t start, phys_addr_t end)
 	if (early_is_tdx_guest()) {
 		if (!tdx_accept_memory(start, end))
 			panic("TDX: Failed to accept memory\n");
+	} else if (sev_snp_enabled()) {
+		snp_accept_memory(start, end);
 	} else {
 		error("Cannot accept memory: unknown platform\n");
 	}
diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c
index 014b89c89088..09dc8c187b3c 100644
--- a/arch/x86/boot/compressed/sev.c
+++ b/arch/x86/boot/compressed/sev.c
@@ -115,7 +115,7 @@ static enum es_result vc_read_mem(struct es_em_ctxt *ctxt,
 /* Include code for early handlers */
 #include "../../kernel/sev-shared.c"
 
-static inline bool sev_snp_enabled(void)
+bool sev_snp_enabled(void)
 {
 	return sev_status & MSR_AMD64_SEV_SNP_ENABLED;
 }
@@ -181,6 +181,58 @@ static bool early_setup_ghcb(void)
 	return true;
 }
 
+static phys_addr_t __snp_accept_memory(struct snp_psc_desc *desc,
+				       phys_addr_t pa, phys_addr_t pa_end)
+{
+	struct psc_hdr *hdr;
+	struct psc_entry *e;
+	unsigned int i;
+
+	hdr = &desc->hdr;
+	memset(hdr, 0, sizeof(*hdr));
+
+	e = desc->entries;
+
+	i = 0;
+	while (pa < pa_end && i < VMGEXIT_PSC_MAX_ENTRY) {
+		hdr->end_entry = i;
+
+		e->gfn = pa >> PAGE_SHIFT;
+		e->operation = SNP_PAGE_STATE_PRIVATE;
+		if (IS_ALIGNED(pa, PMD_SIZE) && (pa_end - pa) >= PMD_SIZE) {
+			e->pagesize = RMP_PG_SIZE_2M;
+			pa += PMD_SIZE;
+		} else {
+			e->pagesize = RMP_PG_SIZE_4K;
+			pa += PAGE_SIZE;
+		}
+
+		e++;
+		i++;
+	}
+
+	if (vmgexit_psc(boot_ghcb, desc))
+		sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_PSC);
+
+	pvalidate_pages(desc);
+
+	return pa;
+}
+
+void snp_accept_memory(phys_addr_t start, phys_addr_t end)
+{
+	struct snp_psc_desc desc = {};
+	unsigned int i;
+	phys_addr_t pa;
+
+	if (!boot_ghcb && !early_setup_ghcb())
+		sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_PSC);
+
+	pa = start;
+	while (pa < end)
+		pa = __snp_accept_memory(&desc, pa, end);
+}
+
 void sev_es_shutdown_ghcb(void)
 {
 	if (!boot_ghcb)
diff --git a/arch/x86/boot/compressed/sev.h b/arch/x86/boot/compressed/sev.h
new file mode 100644
index 000000000000..fc725a981b09
--- /dev/null
+++ b/arch/x86/boot/compressed/sev.h
@@ -0,0 +1,23 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * AMD SEV header for early boot related functions.
+ *
+ * Author: Tom Lendacky <thomas.lendacky@amd.com>
+ */
+
+#ifndef BOOT_COMPRESSED_SEV_H
+#define BOOT_COMPRESSED_SEV_H
+
+#ifdef CONFIG_AMD_MEM_ENCRYPT
+
+bool sev_snp_enabled(void);
+void snp_accept_memory(phys_addr_t start, phys_addr_t end);
+
+#else
+
+static inline bool sev_snp_enabled(void) { return false; }
+static inline void snp_accept_memory(phys_addr_t start, phys_addr_t end) { }
+
+#endif
+
+#endif
diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index e21e1c5397c1..86e1296e87f5 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -206,6 +206,7 @@ void snp_set_wakeup_secondary_cpu(void);
 bool snp_init(struct boot_params *bp);
 void __init __noreturn snp_abort(void);
 int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, struct snp_guest_request_ioctl *rio);
+void snp_accept_memory(phys_addr_t start, phys_addr_t end);
 #else
 static inline void sev_es_ist_enter(struct pt_regs *regs) { }
 static inline void sev_es_ist_exit(void) { }
@@ -229,6 +230,8 @@ static inline int snp_issue_guest_request(u64 exit_code, struct snp_req_data *in
 {
 	return -ENOTTY;
 }
+
+static inline void snp_accept_memory(phys_addr_t start, phys_addr_t end) { }
 #endif
 
 #endif
diff --git a/arch/x86/include/asm/unaccepted_memory.h b/arch/x86/include/asm/unaccepted_memory.h
index 572514e36fde..f5937e9866ac 100644
--- a/arch/x86/include/asm/unaccepted_memory.h
+++ b/arch/x86/include/asm/unaccepted_memory.h
@@ -3,6 +3,7 @@
 
 #include <linux/efi.h>
 #include <asm/tdx.h>
+#include <asm/sev.h>
 
 static inline void arch_accept_memory(phys_addr_t start, phys_addr_t end)
 {
@@ -10,6 +11,8 @@ static inline void arch_accept_memory(phys_addr_t start, phys_addr_t end)
 	if (cpu_feature_enabled(X86_FEATURE_TDX_GUEST)) {
 		if (!tdx_accept_memory(start, end))
 			panic("TDX: Failed to accept memory\n");
+	} else if (cc_platform_has(CC_ATTR_GUEST_SEV_SNP)) {
+		snp_accept_memory(start, end);
 	} else {
 		panic("Cannot accept memory: unknown platform\n");
 	}
diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c
index 3a5b0c9c4fcc..2eabccde94fb 100644
--- a/arch/x86/kernel/sev-shared.c
+++ b/arch/x86/kernel/sev-shared.c
@@ -12,6 +12,9 @@
 #ifndef __BOOT_COMPRESSED
 #define error(v)	pr_err(v)
 #define has_cpuflag(f)	boot_cpu_has(f)
+#else
+#undef WARN
+#define WARN(condition, format...) (!!(condition))
 #endif
 
 /* I/O parameters for CPUID-related helpers */
@@ -991,3 +994,103 @@ static void __init setup_cpuid_table(const struct cc_blob_sev_info *cc_info)
 			cpuid_ext_range_max = fn->eax;
 	}
 }
+
+static void pvalidate_pages(struct snp_psc_desc *desc)
+{
+	struct psc_entry *e;
+	unsigned long vaddr;
+	unsigned int size;
+	unsigned int i;
+	bool validate;
+	int rc;
+
+	for (i = 0; i <= desc->hdr.end_entry; i++) {
+		e = &desc->entries[i];
+
+		vaddr = (unsigned long)pfn_to_kaddr(e->gfn);
+		size = e->pagesize ? RMP_PG_SIZE_2M : RMP_PG_SIZE_4K;
+		validate = e->operation == SNP_PAGE_STATE_PRIVATE;
+
+		rc = pvalidate(vaddr, size, validate);
+		if (rc == PVALIDATE_FAIL_SIZEMISMATCH && size == RMP_PG_SIZE_2M) {
+			unsigned long vaddr_end = vaddr + PMD_SIZE;
+
+			for (; vaddr < vaddr_end; vaddr += PAGE_SIZE) {
+				rc = pvalidate(vaddr, RMP_PG_SIZE_4K, validate);
+				if (rc)
+					break;
+			}
+		}
+
+		if (rc) {
+			WARN(1, "Failed to validate address 0x%lx ret %d", vaddr, rc);
+			sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_PVALIDATE);
+		}
+	}
+}
+
+static int vmgexit_psc(struct ghcb *ghcb, struct snp_psc_desc *desc)
+{
+	int cur_entry, end_entry, ret = 0;
+	struct snp_psc_desc *data;
+	struct es_em_ctxt ctxt;
+
+	vc_ghcb_invalidate(ghcb);
+
+	/* Copy the input desc into GHCB shared buffer */
+	data = (struct snp_psc_desc *)ghcb->shared_buffer;
+	memcpy(ghcb->shared_buffer, desc, min_t(int, GHCB_SHARED_BUF_SIZE, sizeof(*desc)));
+
+	/*
+	 * As per the GHCB specification, the hypervisor can resume the guest
+	 * before processing all the entries. Check whether all the entries
+	 * are processed. If not, then keep retrying. Note, the hypervisor
+	 * will update the data memory directly to indicate the status, so
+	 * reference the data->hdr everywhere.
+	 *
+	 * The strategy here is to wait for the hypervisor to change the page
+	 * state in the RMP table before guest accesses the memory pages. If the
+	 * page state change was not successful, then later memory access will
+	 * result in a crash.
+	 */
+	cur_entry = data->hdr.cur_entry;
+	end_entry = data->hdr.end_entry;
+
+	while (data->hdr.cur_entry <= data->hdr.end_entry) {
+		ghcb_set_sw_scratch(ghcb, (u64)__pa(data));
+
+		/* This will advance the shared buffer data points to. */
+		ret = sev_es_ghcb_hv_call(ghcb, &ctxt, SVM_VMGEXIT_PSC, 0, 0);
+
+		/*
+		 * Page State Change VMGEXIT can pass error code through
+		 * exit_info_2.
+		 */
+		if (WARN(ret || ghcb->save.sw_exit_info_2,
+			 "SNP: PSC failed ret=%d exit_info_2=%llx\n",
+			 ret, ghcb->save.sw_exit_info_2)) {
+			ret = 1;
+			goto out;
+		}
+
+		/* Verify that reserved bit is not set */
+		if (WARN(data->hdr.reserved, "Reserved bit is set in the PSC header\n")) {
+			ret = 1;
+			goto out;
+		}
+
+		/*
+		 * Sanity check that entry processing is not going backwards.
+		 * This will happen only if hypervisor is tricking us.
+		 */
+		if (WARN(data->hdr.end_entry > end_entry || cur_entry > data->hdr.cur_entry,
+"SNP: PSC processing going backward, end_entry %d (got %d) cur_entry %d (got %d)\n",
+			 end_entry, data->hdr.end_entry, cur_entry, data->hdr.cur_entry)) {
+			ret = 1;
+			goto out;
+		}
+	}
+
+out:
+	return ret;
+}
diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index 17b3d003b2ea..ea2546e5130f 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -657,38 +657,6 @@ static u64 __init get_jump_table_addr(void)
 	return ret;
 }
 
-static void pvalidate_pages(struct snp_psc_desc *desc)
-{
-	struct psc_entry *e;
-	unsigned long vaddr;
-	unsigned int size;
-	unsigned int i;
-	bool validate;
-	int rc;
-
-	for (i = 0; i <= desc->hdr.end_entry; i++) {
-		e = &desc->entries[i];
-
-		vaddr = (unsigned long)pfn_to_kaddr(e->gfn);
-		size = e->pagesize ? RMP_PG_SIZE_2M : RMP_PG_SIZE_4K;
-		validate = e->operation == SNP_PAGE_STATE_PRIVATE;
-
-		rc = pvalidate(vaddr, size, validate);
-		if (rc == PVALIDATE_FAIL_SIZEMISMATCH && size == RMP_PG_SIZE_2M) {
-			unsigned long vaddr_end = vaddr + PMD_SIZE;
-
-			for (; vaddr < vaddr_end; vaddr += PAGE_SIZE) {
-				rc = pvalidate(vaddr, RMP_PG_SIZE_4K, validate);
-				if (rc)
-					break;
-			}
-		}
-
-		if (WARN(rc, "Failed to validate address 0x%lx ret %d", vaddr, rc))
-			sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_PVALIDATE);
-	}
-}
-
 static void early_set_pages_state(unsigned long vaddr, unsigned long paddr,
 				  unsigned long npages, enum psc_op op)
 {
@@ -796,72 +764,6 @@ void __init snp_prep_memory(unsigned long paddr, unsigned int sz, enum psc_op op
 		WARN(1, "invalid memory op %d\n", op);
 }
 
-static int vmgexit_psc(struct ghcb *ghcb, struct snp_psc_desc *desc)
-{
-	int cur_entry, end_entry, ret = 0;
-	struct snp_psc_desc *data;
-	struct es_em_ctxt ctxt;
-
-	vc_ghcb_invalidate(ghcb);
-
-	/* Copy the input desc into GHCB shared buffer */
-	data = (struct snp_psc_desc *)ghcb->shared_buffer;
-	memcpy(ghcb->shared_buffer, desc, min_t(int, GHCB_SHARED_BUF_SIZE, sizeof(*desc)));
-
-	/*
-	 * As per the GHCB specification, the hypervisor can resume the guest
-	 * before processing all the entries. Check whether all the entries
-	 * are processed. If not, then keep retrying. Note, the hypervisor
-	 * will update the data memory directly to indicate the status, so
-	 * reference the data->hdr everywhere.
-	 *
-	 * The strategy here is to wait for the hypervisor to change the page
-	 * state in the RMP table before guest accesses the memory pages. If the
-	 * page state change was not successful, then later memory access will
-	 * result in a crash.
-	 */
-	cur_entry = data->hdr.cur_entry;
-	end_entry = data->hdr.end_entry;
-
-	while (data->hdr.cur_entry <= data->hdr.end_entry) {
-		ghcb_set_sw_scratch(ghcb, (u64)__pa(data));
-
-		/* This will advance the shared buffer data points to. */
-		ret = sev_es_ghcb_hv_call(ghcb, &ctxt, SVM_VMGEXIT_PSC, 0, 0);
-
-		/*
-		 * Page State Change VMGEXIT can pass error code through
-		 * exit_info_2.
-		 */
-		if (WARN(ret || ghcb->save.sw_exit_info_2,
-			 "SNP: PSC failed ret=%d exit_info_2=%llx\n",
-			 ret, ghcb->save.sw_exit_info_2)) {
-			ret = 1;
-			goto out;
-		}
-
-		/* Verify that reserved bit is not set */
-		if (WARN(data->hdr.reserved, "Reserved bit is set in the PSC header\n")) {
-			ret = 1;
-			goto out;
-		}
-
-		/*
-		 * Sanity check that entry processing is not going backwards.
-		 * This will happen only if hypervisor is tricking us.
-		 */
-		if (WARN(data->hdr.end_entry > end_entry || cur_entry > data->hdr.cur_entry,
-"SNP: PSC processing going backward, end_entry %d (got %d) cur_entry %d (got %d)\n",
-			 end_entry, data->hdr.end_entry, cur_entry, data->hdr.cur_entry)) {
-			ret = 1;
-			goto out;
-		}
-	}
-
-out:
-	return ret;
-}
-
 static unsigned long __set_pages_state(struct snp_psc_desc *data, unsigned long vaddr,
 				       unsigned long vaddr_end, int op)
 {
@@ -966,6 +868,20 @@ void snp_set_memory_private(unsigned long vaddr, unsigned long npages)
 	set_pages_state(vaddr, npages, SNP_PAGE_STATE_PRIVATE);
 }
 
+void snp_accept_memory(phys_addr_t start, phys_addr_t end)
+{
+	unsigned long vaddr;
+	unsigned int npages;
+
+	if (!cc_platform_has(CC_ATTR_GUEST_SEV_SNP))
+		return;
+
+	vaddr = (unsigned long)__va(start);
+	npages = (end - start) >> PAGE_SHIFT;
+
+	set_pages_state(vaddr, npages, SNP_PAGE_STATE_PRIVATE);
+}
+
 static int snp_set_vmsa(void *va, bool vmsa)
 {
 	u64 attrs;
-- 
2.40.1

> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 5c72067c06d4..b9c451f75d5e 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -1543,11 +1543,13 @@ config X86_MEM_ENCRYPT
>   config AMD_MEM_ENCRYPT
>   	bool "AMD Secure Memory Encryption (SME) support"
>   	depends on X86_64 && CPU_SUP_AMD
> +	depends on EFI_STUB
>   	select DMA_COHERENT_POOL
>   	select ARCH_USE_MEMREMAP_PROT
>   	select INSTRUCTION_DECODER
>   	select ARCH_HAS_CC_PLATFORM
>   	select X86_MEM_ENCRYPT
> +	select UNACCEPTED_MEMORY
>   	help
>   	  Say yes to enable support for the encryption of system memory.
>   	  This requires an AMD processor that supports Secure Memory

Unfortunately this makes AMD_MEM_ENCRYPT depend on EFI just to 
unconditionally enable UNACCEPTED_MEMORY. It seems like an easy target 
to make that optional, e.g. with a separate configuration item:

---
config AMD_UNACCEPTED_MEMORY
        def_bool y
        depends on AMD_MEM_ENCRYPT && EFI_STUB
        select UNACCEPTED_MEMORY
---

Using that we can successfully build and run SNP VMs without UEFI/OVMF 
(which we already did with earlier Linux versions).

 From a quick look at

   [PATCHv14 9/9] x86/tdx: Add unaccepted memory support

it actually seems very similar for INTEL_TDX_GUEST.

Ideally UNACCEPTED_MEMORY would not assume EFI either, but the 
implementation actually clearly does.

On 9/6/23 09:04, Christopher Schramm wrote:
>> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
>> index 5c72067c06d4..b9c451f75d5e 100644
>> --- a/arch/x86/Kconfig
>> +++ b/arch/x86/Kconfig
>> @@ -1543,11 +1543,13 @@ config X86_MEM_ENCRYPT
>>   config AMD_MEM_ENCRYPT
>>       bool "AMD Secure Memory Encryption (SME) support"
>>       depends on X86_64 && CPU_SUP_AMD
>> +    depends on EFI_STUB
>>       select DMA_COHERENT_POOL
>>       select ARCH_USE_MEMREMAP_PROT
>>       select INSTRUCTION_DECODER
>>       select ARCH_HAS_CC_PLATFORM
>>       select X86_MEM_ENCRYPT
>> +    select UNACCEPTED_MEMORY
>>       help
>>         Say yes to enable support for the encryption of system memory.
>>         This requires an AMD processor that supports Secure Memory
> 
> Unfortunately this makes AMD_MEM_ENCRYPT depend on EFI just to 
> unconditionally enable UNACCEPTED_MEMORY. It seems like an easy target to 
> make that optional, e.g. with a separate configuration item:
> 
> ---
> config AMD_UNACCEPTED_MEMORY
>         def_bool y
>         depends on AMD_MEM_ENCRYPT && EFI_STUB
>         select UNACCEPTED_MEMORY
> ---
> 
> Using that we can successfully build and run SNP VMs without UEFI/OVMF 
> (which we already did with earlier Linux versions).

This seems reasonable to me.

I would recommend naming it AMD_MEM_ENCRYPT_UNACCEPTED_MEMORY to keep the 
association and add a prompt along the lines of "AMD Secure Encrypted 
Virtualization (SEV) unaccepted memory support" (I don't really see this 
used with bare-metal, but who knows.)

I think there will need to be changes elsewhere in the kernel to support 
this, though. A quick build test with just AMD_UNACCEPTED_MEMORY not being 
set broke the build when EFI_STUB was still set to y.

> 
>  From a quick look at
> 
>    [PATCHv14 9/9] x86/tdx: Add unaccepted memory support
> 
> it actually seems very similar for INTEL_TDX_GUEST.
> 
> Ideally UNACCEPTED_MEMORY would not assume EFI either, but the 
> implementation actually clearly does.

@Kirill, is this something you are interested in having as well?

Thanks,
Tom

On Thu, Sep 07, 2023 at 11:50:15AM -0500, Tom Lendacky wrote:
> >  From a quick look at
> > 
> >    [PATCHv14 9/9] x86/tdx: Add unaccepted memory support
> > 
> > it actually seems very similar for INTEL_TDX_GUEST.
> > 
> > Ideally UNACCEPTED_MEMORY would not assume EFI either, but the
> > implementation actually clearly does.
> 
> @Kirill, is this something you are interested in having as well?

Unaccepted memory is an EFI feature I don't see how UNACCEPTED_MEMORY can
be untied from EFI. If there's other (non-EFI) environment that has
similar concept, sure we can try to generalize it beyond EFI.

TDX guest is only runs with EFI firmware so far, so depending onf EFI and
EFI_STUB is fine for TDX>

-- 
  Kiryl Shutsemau / Kirill A. Shutemov

On 9/12/23 07:17, Kirill A. Shutemov wrote:
> On Thu, Sep 07, 2023 at 11:50:15AM -0500, Tom Lendacky wrote:
>>>   From a quick look at
>>>
>>>     [PATCHv14 9/9] x86/tdx: Add unaccepted memory support
>>>
>>> it actually seems very similar for INTEL_TDX_GUEST.
>>>
>>> Ideally UNACCEPTED_MEMORY would not assume EFI either, but the
>>> implementation actually clearly does.
>>
>> @Kirill, is this something you are interested in having as well?
> 
> Unaccepted memory is an EFI feature I don't see how UNACCEPTED_MEMORY can
> be untied from EFI. If there's other (non-EFI) environment that has
> similar concept, sure we can try to generalize it beyond EFI.

Sorry, didn't mean to include the EFI related statement there. Agreed that 
unaccepted memory is only an EFI feature right now.

> 
> TDX guest is only runs with EFI firmware so far, so depending onf EFI and
> EFI_STUB is fine for TDX>

Right, SEV initially only ran on EFI firmware, but others have managed to 
get it working in other environments. So I was just wondering if you would 
also want to split the UNACCEPTED_MEMORY out for TDX similar to what was 
suggested for SEV.

Thanks,
Tom

>