arch/x86/hyperv/hv_init.c | 8 ++++++++ arch/x86/include/asm/sev.h | 6 ++++++ arch/x86/kernel/sev-shared.c | 4 ++-- 3 files changed, 16 insertions(+), 2 deletions(-)
From: Tianyu Lan <Tianyu.Lan@microsoft.com>
Hyper-V Isolation VM code uses sev_es_ghcb_hv_call() to read/write MSR
via GHCB page. The SEV-ES guest should negotiate GHCB version before
reading/writing MSR via GHCB page. Expose sev_es_negotiate_protocol()
and sev_es_terminate() from AMD SEV code and negotiate GHCB version in
hyperv_init_ghcb() fro Hyper-V Isolation VM.
Signed-off-by: Tianyu Lan <Tianyu.Lan@microsoft.com>
---
arch/x86/hyperv/hv_init.c | 8 ++++++++
arch/x86/include/asm/sev.h | 6 ++++++
arch/x86/kernel/sev-shared.c | 4 ++--
3 files changed, 16 insertions(+), 2 deletions(-)
diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 8b392b6b7b93..56e2c34e7d64 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -29,6 +29,7 @@
#include <clocksource/hyperv_timer.h>
#include <linux/highmem.h>
#include <linux/swiotlb.h>
+#include <asm/sev.h>
int hyperv_init_cpuhp;
u64 hv_current_partition_id = ~0ull;
@@ -70,6 +71,13 @@ static int hyperv_init_ghcb(void)
ghcb_base = (void **)this_cpu_ptr(hv_ghcb_pg);
*ghcb_base = ghcb_va;
+ /* Negotiate GHCB Version. */
+ if (!sev_es_negotiate_protocol())
+ sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SEV_ES_PROT_UNSUPPORTED);
+
+ /* Write ghcb page back after negotiating protocol. */
+ wrmsrl(MSR_AMD64_SEV_ES_GHCB, ghcb_gpa);
+ VMGEXIT();
return 0;
}
diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index 19514524f0f8..ad69c1dc081b 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -161,6 +161,9 @@ extern enum es_result sev_es_ghcb_hv_call(struct ghcb *ghcb,
struct es_em_ctxt *ctxt,
u64 exit_code, u64 exit_info_1,
u64 exit_info_2);
+extern bool sev_es_negotiate_protocol(void);
+extern void sev_es_terminate(unsigned int set, unsigned int reason);
+
static inline int rmpadjust(unsigned long vaddr, bool rmp_psize, unsigned long attrs)
{
int rc;
@@ -226,6 +229,9 @@ static inline int snp_issue_guest_request(u64 exit_code, struct snp_req_data *in
{
return -ENOTTY;
}
+
+static bool sev_es_negotiate_protocol(void) { return false; }
+static void sev_es_terminate(unsigned int set, unsigned int reason) { }
#endif
#endif
diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c
index 2b4270d5559e..bffc38f0d5ed 100644
--- a/arch/x86/kernel/sev-shared.c
+++ b/arch/x86/kernel/sev-shared.c
@@ -86,7 +86,7 @@ static bool __init sev_es_check_cpu_features(void)
return true;
}
-static void __noreturn sev_es_terminate(unsigned int set, unsigned int reason)
+void __noreturn sev_es_terminate(unsigned int set, unsigned int reason)
{
u64 val = GHCB_MSR_TERM_REQ;
@@ -137,7 +137,7 @@ static void snp_register_ghcb_early(unsigned long paddr)
sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_REGISTER);
}
-static bool sev_es_negotiate_protocol(void)
+bool sev_es_negotiate_protocol(void)
{
u64 val;
--
2.25.1On Thu, May 05, 2022 at 09:15:02AM -0400, Tianyu Lan wrote:
> From: Tianyu Lan <Tianyu.Lan@microsoft.com>
>
> Hyper-V Isolation VM code uses sev_es_ghcb_hv_call() to read/write MSR
> via GHCB page. The SEV-ES guest should negotiate GHCB version before
> reading/writing MSR via GHCB page.
Why is that?
> Expose sev_es_negotiate_protocol() and sev_es_terminate() from AMD SEV
> code
Yeah, you keep wanting to expose random SEV-specific code and when we
go and change it in the future, you'll come complaining that we broke
hyperv.
I think it might be a lot better if you implement your own functions:
for example, looking at sev_es_negotiate_protocol() - it uses only
primitives which you can use because, well, VMGEXIT() is simply a
wrapper around the asm insn and sev_es_wr_ghcb_msr() is simply writing
into the MSR.
Ditto for sev_es_terminate().
And sev_es_ghcb_hv_call() too, for that matter. You can define your own.
IOW, you're much better off using those primitives and creating your own
functions than picking out random SEV-functions and then us breaking
your isolation VM stuff.
Thx.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
On 5/10/2022 6:48 AM, Borislav Petkov wrote: > On Thu, May 05, 2022 at 09:15:02AM -0400, Tianyu Lan wrote: >> From: Tianyu Lan <Tianyu.Lan@microsoft.com> >> >> Hyper-V Isolation VM code uses sev_es_ghcb_hv_call() to read/write MSR >> via GHCB page. The SEV-ES guest should negotiate GHCB version before >> reading/writing MSR via GHCB page. > > Why is that? > >> Expose sev_es_negotiate_protocol() and sev_es_terminate() from AMD SEV >> code > > Yeah, you keep wanting to expose random SEV-specific code and when we > go and change it in the future, you'll come complaining that we broke > hyperv. > > I think it might be a lot better if you implement your own functions: > for example, looking at sev_es_negotiate_protocol() - it uses only > primitives which you can use because, well, VMGEXIT() is simply a > wrapper around the asm insn and sev_es_wr_ghcb_msr() is simply writing > into the MSR. > > Ditto for sev_es_terminate(). > > And sev_es_ghcb_hv_call() too, for that matter. You can define your own. > > IOW, you're much better off using those primitives and creating your own > functions than picking out random SEV-functions and then us breaking > your isolation VM stuff. > OK. I got it. Thanks for your suggestion.
On Thu, May 05, 2022 at 09:15:02AM -0400, Tianyu Lan wrote:
> From: Tianyu Lan <Tianyu.Lan@microsoft.com>
>
> Hyper-V Isolation VM code uses sev_es_ghcb_hv_call() to read/write MSR
> via GHCB page. The SEV-ES guest should negotiate GHCB version before
> reading/writing MSR via GHCB page. Expose sev_es_negotiate_protocol()
> and sev_es_terminate() from AMD SEV code and negotiate GHCB version in
> hyperv_init_ghcb() fro Hyper-V Isolation VM.
>
> Signed-off-by: Tianyu Lan <Tianyu.Lan@microsoft.com>
Applied to tip's x86/sev and checked that this can fix the regression (to
be introduced) by commit 2ea29c5abbc2 ("x86/sev: Save the negotiated GHCB
version"):
Tested-by: Andrea Parri (Microsoft) <parri.andrea@gmail.com>
Nits: (in the commit message) fro -> for, Isolation VM -> Isolated VM
Thanks,
Andrea
> ---
> arch/x86/hyperv/hv_init.c | 8 ++++++++
> arch/x86/include/asm/sev.h | 6 ++++++
> arch/x86/kernel/sev-shared.c | 4 ++--
> 3 files changed, 16 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> index 8b392b6b7b93..56e2c34e7d64 100644
> --- a/arch/x86/hyperv/hv_init.c
> +++ b/arch/x86/hyperv/hv_init.c
> @@ -29,6 +29,7 @@
> #include <clocksource/hyperv_timer.h>
> #include <linux/highmem.h>
> #include <linux/swiotlb.h>
> +#include <asm/sev.h>
>
> int hyperv_init_cpuhp;
> u64 hv_current_partition_id = ~0ull;
> @@ -70,6 +71,13 @@ static int hyperv_init_ghcb(void)
> ghcb_base = (void **)this_cpu_ptr(hv_ghcb_pg);
> *ghcb_base = ghcb_va;
>
> + /* Negotiate GHCB Version. */
> + if (!sev_es_negotiate_protocol())
> + sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SEV_ES_PROT_UNSUPPORTED);
> +
> + /* Write ghcb page back after negotiating protocol. */
> + wrmsrl(MSR_AMD64_SEV_ES_GHCB, ghcb_gpa);
> + VMGEXIT();
> return 0;
> }
>
> diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
> index 19514524f0f8..ad69c1dc081b 100644
> --- a/arch/x86/include/asm/sev.h
> +++ b/arch/x86/include/asm/sev.h
> @@ -161,6 +161,9 @@ extern enum es_result sev_es_ghcb_hv_call(struct ghcb *ghcb,
> struct es_em_ctxt *ctxt,
> u64 exit_code, u64 exit_info_1,
> u64 exit_info_2);
> +extern bool sev_es_negotiate_protocol(void);
> +extern void sev_es_terminate(unsigned int set, unsigned int reason);
> +
> static inline int rmpadjust(unsigned long vaddr, bool rmp_psize, unsigned long attrs)
> {
> int rc;
> @@ -226,6 +229,9 @@ static inline int snp_issue_guest_request(u64 exit_code, struct snp_req_data *in
> {
> return -ENOTTY;
> }
> +
> +static bool sev_es_negotiate_protocol(void) { return false; }
> +static void sev_es_terminate(unsigned int set, unsigned int reason) { }
> #endif
>
> #endif
> diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c
> index 2b4270d5559e..bffc38f0d5ed 100644
> --- a/arch/x86/kernel/sev-shared.c
> +++ b/arch/x86/kernel/sev-shared.c
> @@ -86,7 +86,7 @@ static bool __init sev_es_check_cpu_features(void)
> return true;
> }
>
> -static void __noreturn sev_es_terminate(unsigned int set, unsigned int reason)
> +void __noreturn sev_es_terminate(unsigned int set, unsigned int reason)
> {
> u64 val = GHCB_MSR_TERM_REQ;
>
> @@ -137,7 +137,7 @@ static void snp_register_ghcb_early(unsigned long paddr)
> sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_REGISTER);
> }
>
> -static bool sev_es_negotiate_protocol(void)
> +bool sev_es_negotiate_protocol(void)
> {
> u64 val;
>
> --
> 2.25.1
>
On 5/5/2022 11:47 PM, Andrea Parri wrote:
> On Thu, May 05, 2022 at 09:15:02AM -0400, Tianyu Lan wrote:
>> From: Tianyu Lan <Tianyu.Lan@microsoft.com>
>>
>> Hyper-V Isolation VM code uses sev_es_ghcb_hv_call() to read/write MSR
>> via GHCB page. The SEV-ES guest should negotiate GHCB version before
>> reading/writing MSR via GHCB page. Expose sev_es_negotiate_protocol()
>> and sev_es_terminate() from AMD SEV code and negotiate GHCB version in
>> hyperv_init_ghcb() fro Hyper-V Isolation VM.
>>
>> Signed-off-by: Tianyu Lan <Tianyu.Lan@microsoft.com>
>
> Applied to tip's x86/sev and checked that this can fix the regression (to
> be introduced) by commit 2ea29c5abbc2 ("x86/sev: Save the negotiated GHCB
> version"):
>
> Tested-by: Andrea Parri (Microsoft) <parri.andrea@gmail.com>
>
> Nits: (in the commit message) fro -> for, Isolation VM -> Isolated VM
>
Nice catch! Thanks.
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