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Wed, 05 Aug 2026 02:24:53 -0700 (PDT) Message-ID: <2ccead84-eaa4-428a-8684-da26874c05e9@suse.com> Date: Wed, 5 Aug 2026 11:24:52 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: [PATCH v10 6/6] VMX: support MSR-IMM From: Jan Beulich To: "xen-devel@lists.xenproject.org" Cc: Andrew Cooper , Teddy Astie , =?UTF-8?Q?Roger_Pau_Monn=C3=A9?= References: <81a2c636-5a74-41c3-81a2-3f49ed717744@suse.com> 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 In-Reply-To: <81a2c636-5a74-41c3-81a2-3f49ed717744@suse.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-purgate-ID: tlsNG-d25034/1785921894-00ACCA5B-A4C27296/0/0 X-purgate-type: clean X-purgate-size: 4687 Hook up the new VM exit codes and handle guest uses of the insns. Signed-off-by: Jan Beulich --- v10: Check feature bit in exit handler. v9: New. --- The lack of an enable bit is concerning; at least for the nested case that's a security issue afaict (when L0 isn't aware of the insns, or more specifically the exit codes). --- a/xen/arch/x86/cpu-policy.c +++ b/xen/arch/x86/cpu-policy.c @@ -834,10 +834,11 @@ static void __init calculate_hvm_max_pol __clear_bit(X86_FEATURE_PKS, fs); /* - * Don't expose USER-MSR until it is known how (if at all) it is - * virtualized on SVM. + * Don't expose USER-MSR and MSR-IMM until it is known how (if at all) + * they are virtualized on SVM. */ __clear_bit(X86_FEATURE_USER_MSR, fs); + __clear_bit(X86_FEATURE_MSR_IMM, fs); } if ( !cpu_has_vmx_msrlist ) --- a/xen/arch/x86/domain.c +++ b/xen/arch/x86/domain.c @@ -453,7 +453,7 @@ void domain_cpu_policy_changed(struct do } /* Nested doesn't have the necessary processing, yet. */ - if ( nestedhvm_enabled(d) && p->feat.user_msr ) + if ( nestedhvm_enabled(d) && (p->feat.user_msr || p->feat.msr_imm) ) return /* -EINVAL */; for_each_vcpu ( d, v ) --- a/xen/arch/x86/hvm/vmx/vmx.c +++ b/xen/arch/x86/hvm/vmx/vmx.c @@ -4712,6 +4712,14 @@ void asmlinkage vmx_vmexit_handler(struc hvm_inject_hw_exception(X86_EXC_GP, 0); break; + case EXIT_REASON_RDMSR_IMM: + /* Check the feature bit in lieu of an enable one. */ + if ( !currd->arch.cpuid->feat.msr_imm ) + { + hvm_inject_hw_exception(X86_EXC_UD, X86_EVENT_NO_EC); + break; + } + fallthrough; case EXIT_REASON_URDMSR: /* NB: User-MSR bitmap was checked by the CPU. */ { uint64_t msr_content = 0; @@ -4721,7 +4729,7 @@ void asmlinkage vmx_vmexit_handler(struc { case X86EMUL_OKAY: *decode_gpr(regs, msr_imm_gpr()) = msr_content; - update_guest_eip(); /* Safe: URDMSR */ + update_guest_eip(); /* Safe: URDMSR / RDMSR */ break; case X86EMUL_EXCEPTION: @@ -4731,6 +4739,14 @@ void asmlinkage vmx_vmexit_handler(struc break; } + case EXIT_REASON_WRMSRNS_IMM: + /* Check the feature bit in lieu of an enable one. */ + if ( !currd->arch.cpuid->feat.msr_imm ) + { + hvm_inject_hw_exception(X86_EXC_UD, X86_EVENT_NO_EC); + break; + } + fallthrough; case EXIT_REASON_UWRMSR: /* NB: User-MSR bitmap was checked by the CPU. */ exit_qualification = vmread(EXIT_QUALIFICATION); switch ( hvm_msr_write_intercept(exit_qualification, @@ -4738,7 +4754,7 @@ void asmlinkage vmx_vmexit_handler(struc true) ) { case X86EMUL_OKAY: - update_guest_eip(); /* Safe: UWRMSR */ + update_guest_eip(); /* Safe: UWRMSR / WRMSRNS */ break; case X86EMUL_EXCEPTION: --- a/xen/arch/x86/include/asm/hvm/vmx/vmx.h +++ b/xen/arch/x86/include/asm/hvm/vmx/vmx.h @@ -205,6 +205,8 @@ static inline void pi_clear_sn(struct pi #define EXIT_REASON_WRMSRLIST 79 #define EXIT_REASON_URDMSR 80 #define EXIT_REASON_UWRMSR 81 +#define EXIT_REASON_RDMSR_IMM 84 +#define EXIT_REASON_WRMSRNS_IMM 85 /* Remember to also update VMX_PERF_EXIT_REASON_SIZE! */ /* --- a/xen/arch/x86/include/asm/perfc_defn.h +++ b/xen/arch/x86/include/asm/perfc_defn.h @@ -6,7 +6,7 @@ PERFCOUNTER_ARRAY(exceptions, #ifdef CONFIG_HVM -#define VMX_PERF_EXIT_REASON_SIZE 82 +#define VMX_PERF_EXIT_REASON_SIZE 86 #define VMEXIT_NPF_PERFC 166 #define SVM_PERF_EXIT_REASON_SIZE (VMEXIT_NPF_PERFC + 1) PERFCOUNTER_ARRAY(vmexits, "vmexits", --- a/xen/include/public/arch-x86/cpufeatureset.h +++ b/xen/include/public/arch-x86/cpufeatureset.h @@ -354,7 +354,7 @@ XEN_CPUFEATURE(MCDT_NO, 13*32 XEN_CPUFEATURE(UC_LOCK_DIS, 13*32+ 6) /* UC-lock disable */ /* Intel-defined CPU features, CPUID level 0x00000007:1.ecx, word 14 */ -XEN_CPUFEATURE(MSR_IMM, 14*32+ 5) /* RDMSR/WRMSRNS with immediate operand */ +XEN_CPUFEATURE(MSR_IMM, 14*32+ 5) /*s RDMSR/WRMSRNS with immediate operand */ /* Intel-defined CPU features, CPUID level 0x00000007:1.edx, word 15 */ XEN_CPUFEATURE(AVX_VNNI_INT8, 15*32+ 4) /*A AVX-VNNI-INT8 Instructions */