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Mon, 27 Jul 2026 03:29:35 -0700 (PDT) Message-ID: Date: Mon, 27 Jul 2026 12:29:34 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird From: Jan Beulich Subject: [PATCH v2] x86/PV: avoid HVM-copying alternatives in PV-only code To: "xen-devel@lists.xenproject.org" Cc: Andrew Cooper , =?UTF-8?Q?Roger_Pau_Monn=C3=A9?= , Teddy Astie Content-Language: en-US Autocrypt: addr=jbeulich@suse.com; keydata= xsDiBFk3nEQRBADAEaSw6zC/EJkiwGPXbWtPxl2xCdSoeepS07jW8UgcHNurfHvUzogEq5xk hu507c3BarVjyWCJOylMNR98Yd8VqD9UfmX0Hb8/BrA+Hl6/DB/eqGptrf4BSRwcZQM32aZK 7Pj2XbGWIUrZrd70x1eAP9QE3P79Y2oLrsCgbZJfEwCgvz9JjGmQqQkRiTVzlZVCJYcyGGsD /0tbFCzD2h20ahe8rC1gbb3K3qk+LpBtvjBu1RY9drYk0NymiGbJWZgab6t1jM7sk2vuf0Py O9Hf9XBmK0uE9IgMaiCpc32XV9oASz6UJebwkX+zF2jG5I1BfnO9g7KlotcA/v5ClMjgo6Gl MDY4HxoSRu3i1cqqSDtVlt+AOVBJBACrZcnHAUSuCXBPy0jOlBhxPqRWv6ND4c9PH1xjQ3NP nxJuMBS8rnNg22uyfAgmBKNLpLgAGVRMZGaGoJObGf72s6TeIqKJo/LtggAS9qAUiuKVnygo 3wjfkS9A3DRO+SpU7JqWdsveeIQyeyEJ/8PTowmSQLakF+3fote9ybzd880fSmFuIEJldWxp Y2ggPGpiZXVsaWNoQHN1c2UuY29tPsJgBBMRAgAgBQJZN5xEAhsDBgsJCAcDAgQVAggDBBYC AwECHgECF4AACgkQoDSui/t3IH4J+wCfQ5jHdEjCRHj23O/5ttg9r9OIruwAn3103WUITZee e7Sbg12UgcQ5lv7SzsFNBFk3nEQQCACCuTjCjFOUdi5Nm244F+78kLghRcin/awv+IrTcIWF hUpSs1Y91iQQ7KItirz5uwCPlwejSJDQJLIS+QtJHaXDXeV6NI0Uef1hP20+y8qydDiVkv6l IreXjTb7DvksRgJNvCkWtYnlS3mYvQ9NzS9PhyALWbXnH6sIJd2O9lKS1Mrfq+y0IXCP10eS FFGg+Av3IQeFatkJAyju0PPthyTqxSI4lZYuJVPknzgaeuJv/2NccrPvmeDg6Coe7ZIeQ8Yj t0ARxu2xytAkkLCel1Lz1WLmwLstV30g80nkgZf/wr+/BXJW/oIvRlonUkxv+IbBM3dX2OV8 AmRv1ySWPTP7AAMFB/9PQK/VtlNUJvg8GXj9ootzrteGfVZVVT4XBJkfwBcpC/XcPzldjv+3 HYudvpdNK3lLujXeA5fLOH+Z/G9WBc5pFVSMocI71I8bT8lIAzreg0WvkWg5V2WZsUMlnDL9 mpwIGFhlbM3gfDMs7MPMu8YQRFVdUvtSpaAs8OFfGQ0ia3LGZcjA6Ik2+xcqscEJzNH+qh8V m5jjp28yZgaqTaRbg3M/+MTbMpicpZuqF4rnB0AQD12/3BNWDR6bmh+EkYSMcEIpQmBM51qM EKYTQGybRCjpnKHGOxG0rfFY1085mBDZCH5Kx0cl0HVJuQKC+dV2ZY5AqjcKwAxpE75MLFkr wkkEGBECAAkFAlk3nEQCGwwACgkQoDSui/t3IH7nnwCfcJWUDUFKdCsBH/E5d+0ZnMQi+G0A nAuWpQkjM1ASeQwSHEeAWPgskBQL Content-Transfer-Encoding: quoted-printable X-purgate-ID: tlsNG-42698a/1785148176-1B2DC9EA-EFA468EA/0/0 X-purgate-type: clean X-purgate-size: 5001 X-ZohoMail-DKIM: pass (identity @suse.com) X-ZM-MESSAGEID: 1785148198758158500 Content-Type: text/plain; charset="utf-8" x86/PV: avoid HVM-copying alternatives in PV-only code raw_copy_*_guest*() expanding to both a HVM and a PV alternative leaves a lot of unreachable code, violating Misra C:2012 rule 2.1 (without Eclair being able to spot this). Introduce a mechanism to avoid that in handling of PV-only hypercalls (i.e. ones which only PV domains can issue and which only act on PV domains [or which are not domain related]). Signed-off-by: Jan Beulich --- In my default test build this reduces overall code size by almost 2k, and that's with PV_SHIM=3Dn. RFC: The HVM-only enabling is just in case; right now it doesn't look as if that would actually be usable anywhere. Overriding is_hvm_vcpu() (and/or is_hvm_domain()) of course has yet better effects, which pv/shim.c shows particularly well. Yet Misra won't like us doing so. --- v2: Rename manifest constants. Also change raw_clear_guest(). Drop kexec change. --- a/xen/arch/x86/compat.c +++ b/xen/arch/x86/compat.c @@ -5,6 +5,8 @@ * hypercall after doing necessary argument munging. */ =20 +#define GUEST_ACCESS_PV true + #include #include #include --- a/xen/arch/x86/cpu/mcheck/mce.c +++ b/xen/arch/x86/cpu/mcheck/mce.c @@ -1262,6 +1262,8 @@ static void cf_check __maybe_unused x86_ =20 #ifdef CONFIG_PV /* do_mca() hypercall is PV-only */ =20 +#define GUEST_ACCESS_PV true + #if BITS_PER_LONG =3D=3D 64 =20 /* Two layers of casting to cover Misra C:2012 rule 11.2. */ @@ -1666,6 +1668,8 @@ long do_mca(XEN_GUEST_HANDLE_PARAM(xen_m return ret; } =20 +#undef GUEST_ACCESS_PV + #endif /* CONFIG_PV */ =20 static int mcinfo_dumped; --- a/xen/arch/x86/include/asm/guest_access.h +++ b/xen/arch/x86/include/asm/guest_access.h @@ -12,25 +12,30 @@ #include #include =20 +#define IS_HVM_ACCESS \ + (IS_ENABLED(GUEST_ACCESS_HVM) || \ + (!IS_ENABLED(GUEST_ACCESS_PV) && \ + is_hvm_vcpu(current))) \ + /* Raw access functions: no type checking. */ #define raw_copy_to_guest(dst, src, len) \ - (is_hvm_vcpu(current) ? \ + (IS_HVM_ACCESS ? \ copy_to_user_hvm((dst), (src), (len)) : \ copy_to_guest_pv(dst, src, len)) #define raw_copy_from_guest(dst, src, len) \ - (is_hvm_vcpu(current) ? \ + (IS_HVM_ACCESS ? \ copy_from_user_hvm((dst), (src), (len)) : \ copy_from_guest_pv(dst, src, len)) #define raw_clear_guest(dst, len) \ - (is_hvm_vcpu(current) ? \ + (IS_HVM_ACCESS ? \ clear_user_hvm((dst), (len)) : \ clear_guest_pv(dst, len)) #define __raw_copy_to_guest(dst, src, len) \ - (is_hvm_vcpu(current) ? \ + (IS_HVM_ACCESS ? \ copy_to_user_hvm((dst), (src), (len)) : \ __copy_to_guest_pv(dst, src, len)) #define __raw_copy_from_guest(dst, src, len) \ - (is_hvm_vcpu(current) ? \ + (IS_HVM_ACCESS ? \ copy_from_user_hvm((dst), (src), (len)) : \ __copy_from_guest_pv(dst, src, len)) =20 --- a/xen/arch/x86/mm.c +++ b/xen/arch/x86/mm.c @@ -3407,6 +3407,9 @@ int new_guest_cr3(mfn_t mfn) #endif =20 #ifdef CONFIG_PV + +#define GUEST_ACCESS_PV true + static int vcpumask_to_pcpumask( struct domain *d, XEN_GUEST_HANDLE_PARAM(const_void) bmap, cpumask_t *= pmask) { @@ -3447,6 +3450,8 @@ static int vcpumask_to_pcpumask( } } =20 +#undef GUEST_ACCESS_PV + long do_mmuext_op( XEN_GUEST_HANDLE_PARAM(mmuext_op_t) uops, unsigned int count, @@ -3983,6 +3988,8 @@ long do_mmuext_op( return rc; } =20 +#define GUEST_ACCESS_PV true + long do_mmu_update( XEN_GUEST_HANDLE_PARAM(mmu_update_t) ureqs, unsigned int count, @@ -4361,6 +4368,9 @@ long do_mmu_update( =20 return rc; } + +#undef GUEST_ACCESS_PV + #endif /* CONFIG_PV */ =20 /* --- a/xen/arch/x86/pv/callback.c +++ b/xen/arch/x86/pv/callback.c @@ -5,6 +5,8 @@ * hypercall handles and helper functions for guest callback */ =20 +#define GUEST_ACCESS_PV true + #include #include #include --- a/xen/arch/x86/pv/descriptor-tables.c +++ b/xen/arch/x86/pv/descriptor-tables.c @@ -8,6 +8,8 @@ * Copyright (c) 2004 Christian Limpach */ =20 +#define GUEST_ACCESS_PV true + #include #include =20 --- a/xen/arch/x86/pv/shim.c +++ b/xen/arch/x86/pv/shim.c @@ -6,6 +6,9 @@ * * Copyright (c) 2017 Citrix Systems Ltd. */ + +#define GUEST_ACCESS_PV true + #include #include #include