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[37.24.206.209]) by smtp.gmail.com with ESMTPSA id h4-20020a1709063b4400b00a433f470cf1sm648666ejf.138.2024.02.29.04.47.49 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 29 Feb 2024 04:47:49 -0800 (PST) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: bf60a643-d700-11ee-a1ee-f123f15fe8a2 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=google; t=1709210870; x=1709815670; darn=lists.xenproject.org; h=content-transfer-encoding:in-reply-to:autocrypt:from:references:cc :to:content-language:subject:user-agent:mime-version:date:message-id :from:to:cc:subject:date:message-id:reply-to; bh=5Ze8Gl+c5m0bhaEc2tOK4/IUPw2m7dVfUmIkxjX/BKw=; b=XYfguade4+qeZFAfM0OMGR1/X3R7QiD4I7DjlQ8r3Njip3lwpmK17+J5Dy6fx2AUN8 4vCqdqzIffNCvZmygelP8ODow2N2Ab374I7MIVNVlaQRSW5GKVg6MFAhLZUd2++JXyRf XR5Lpl14ivNZbJxxRFbm7GZaeqfbI7ZGkfmuvvJodzougmmf44LYzB4lM6wXQslhyCj+ 1aI85vKnYcPkvnO1leklw7dGexWTVmcPXrKNQmexqfmmjWzqu4DsilAMlvZerEyDmS8h XYz45zq/ej2FeEfwdoItbTcLIPG3cQlRISQTC/NfI63lCJgGDYc8nmUpZilR0ru59g1e KkKA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1709210870; x=1709815670; h=content-transfer-encoding:in-reply-to:autocrypt:from:references:cc :to:content-language:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=5Ze8Gl+c5m0bhaEc2tOK4/IUPw2m7dVfUmIkxjX/BKw=; b=lXMpfJ9CYevgJD2KIQ2Yjl7aJ8hWBEDG2uEIhEqxHaIMsyFlEbDkm7Vxu1MlJn7krD KMHZzu4ryODg5lyp4PIDsiAwJCnW90y1gGuRWTmsgzQNa0PK4lSrCSu6mLRtoGmKHm0w tFcJdttvWuMkvbOuaNCsR6fdI2cMPekhuFFkTXEPpsHQ+u+vydYPdc1aEYe0sty0GTD8 PB81++ZzYwkPYb9x7zhs6eKTpG+rTogXxl1Xg9pCvO3wld8LO9pqOCBeJaAmc4SaB/ZS kNm+37LnNyBVIBNFJAzAI6MbVOC6J+4iCqkpEjmYM3aHDdi0l6bJjurU8NcARdsZ5WVR 5Flg== X-Forwarded-Encrypted: i=1; AJvYcCXFtfOSoYvyreiEb9LwFpQuK3rurQZw3VxJHdebIWM7K0pNJVuuBtgylhBi7p6WlXJ/9Jp7OIRUhlSI5og3gVJeVghfZz5dFxZKGZeo5b4= X-Gm-Message-State: AOJu0Yxt2C+3jAAlbyeyR4MVAE7fkz+ZUZs/3yFUNtHeNx0BvzvESlWq rJOMtwkZXmHmz/ldv+lSeddGdEnX3FgnpzeiXs3Cx62FopLlIzXI67OeOiiM5v2r6aKpR4B4pE4 = X-Google-Smtp-Source: AGHT+IFHn201zo35Usxx1CqEBgm4c8z9VNJgcf4hmP7t39TBbHGV2rQCACoTcW5zSsbZYppIjwZ6Eg== X-Received: by 2002:a17:906:aeca:b0:a43:4e75:21ac with SMTP id me10-20020a170906aeca00b00a434e7521acmr1299893ejb.52.1709210870132; Thu, 29 Feb 2024 04:47:50 -0800 (PST) Message-ID: <707ff486-b448-4bc0-be7e-1c692b360734@suse.com> Date: Thu, 29 Feb 2024 13:47:48 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] x86/cpu-policy: Fix x2APIC visibility for PV guests Content-Language: en-US To: Andrew Cooper Cc: =?UTF-8?Q?Roger_Pau_Monn=C3=A9?= , Wei Liu , Xen-devel References: <20240229104304.2478614-1-andrew.cooper3@citrix.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: <20240229104304.2478614-1-andrew.cooper3@citrix.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 29.02.2024 11:43, Andrew Cooper wrote: > Right now, the host x2APIC setting filters into the PV max and default > policies, yet PV guests cannot set MSR_APIC_BASE.EXTD or access any of the > x2APIC MSR range. Therefore they absolutely shouldn't see the x2APIC bit. > > Linux has workarounds for the collateral damage caused by this leakage; it > unconditionally filters out the x2APIC CPUID bit, and EXTD when reading > MSR_APIC_BASE. > > Hide the x2APIC bit in the PV default policy, but for compatibility, tolerate > incoming VMs which already saw the bit. This is logic from before the > default/max split in Xen 4.14 which wasn't correctly adjusted at the time. What about guest_cpuid()'s handling of leaf 0xb then? The %edx value will change once a guest is rebooted, aiui. The comment in recalculate_cpuid_policy() that you update refers to that. > Update the annotation from !A to !S which slightly better describes that it > doesn't really exist in PV guests. HVM guests, for which x2APIC can be > emulated completely, already has it unconditionally set in the max policy. > > Signed-off-by: Andrew Cooper > --- > CC: Jan Beulich > CC: Roger Pau Monné > CC: Wei Liu > > This wants backporting as far as people can tollerate, but it's really not > obvious which commit in 4.14 should be referenced in a Fixes: tag. Why 4.14? In 4.7.0 I see ... > @@ -830,11 +846,10 @@ void recalculate_cpuid_policy(struct domain *d) > } > > /* > - * Allow the toolstack to set HTT, X2APIC and CMP_LEGACY. These bits > + * Allow the toolstack to set HTT and CMP_LEGACY. These bits > * affect how to interpret topology information in other cpuid leaves. > */ > __set_bit(X86_FEATURE_HTT, max_fs); > - __set_bit(X86_FEATURE_X2APIC, max_fs); > __set_bit(X86_FEATURE_CMP_LEGACY, max_fs); > > /* ... these adjustments, just still in calculate_pv_featureset(). I haven't gone further backwards to check if/when this exposure has really appeared. I wouldn't be surprised if it's been like that for all the time since we gained x2APIC support in the hypervisor. Jan