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Thu, 15 Feb 2024 08:07:52 -0800 (PST) Message-ID: <67306bde-9877-4d6d-a964-3ea964256ce4@suse.com> Date: Thu, 15 Feb 2024 17:07:51 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] x86/vmx: add support for virtualize SPEC_CTRL Content-Language: en-US To: =?UTF-8?Q?Roger_Pau_Monn=C3=A9?= Cc: Jun Nakajima , Kevin Tian , Andrew Cooper , Wei Liu , xen-devel@lists.xenproject.org References: <20240209114045.97005-1-roger.pau@citrix.com> <09cf678e-bdbd-47a9-8c9d-533e7bee9450@suse.com> From: Jan Beulich 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: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 15.02.2024 16:54, Roger Pau Monné wrote: > On Mon, Feb 12, 2024 at 03:09:01PM +0100, Jan Beulich wrote: >> On 09.02.2024 12:40, Roger Pau Monne wrote: >>> --- a/xen/arch/x86/hvm/vmx/vmx.c >>> +++ b/xen/arch/x86/hvm/vmx/vmx.c >>> @@ -823,18 +823,29 @@ static void cf_check vmx_cpuid_policy_changed(struct vcpu *v) >>> { >>> vmx_clear_msr_intercept(v, MSR_SPEC_CTRL, VMX_MSR_RW); >>> >>> - rc = vmx_add_guest_msr(v, MSR_SPEC_CTRL, 0); >>> - if ( rc ) >>> - goto out; >>> + if ( !cpu_has_vmx_virt_spec_ctrl ) >>> + { >>> + rc = vmx_add_guest_msr(v, MSR_SPEC_CTRL, 0); >>> + if ( rc ) >>> + goto out; >>> + } >>> } >>> else >>> { >>> vmx_set_msr_intercept(v, MSR_SPEC_CTRL, VMX_MSR_RW); >>> >>> - rc = vmx_del_msr(v, MSR_SPEC_CTRL, VMX_MSR_GUEST); >>> - if ( rc && rc != -ESRCH ) >>> - goto out; >>> - rc = 0; /* Tolerate -ESRCH */ >>> + /* >>> + * NB: there's no need to clear the virtualize SPEC_CTRL control, as >>> + * the MSR intercept takes precedence. The SPEC_CTRL shadow VMCS field >>> + * is also not loaded on guest entry/exit if the intercept is set. >>> + */ >> >> It wasn't so much the shadow field than the mask one that I was concerned >> might be used in some way. The shadow one clearly is used only during >> guest RDMSR/WRMSR processing. To not focus on "shadow", maybe simple say >> "The SPEC_CTRL shadow VMCS fields are also not ..."? > > What about: > > "The SPEC_CTRL shadow and mask VMCS fields don't take effect if the > intercept is set." SGTM. Jan