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[37.24.206.209]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a5a1787c63bsm1949324766b.51.2024.05.23.08.09.46 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 23 May 2024 08:09:46 -0700 (PDT) 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: 7e9464ad-1916-11ef-b4bb-af5377834399 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=google; t=1716476987; x=1717081787; darn=lists.xenproject.org; h=content-transfer-encoding:in-reply-to:autocrypt:from :content-language:references:cc:to:subject:user-agent:mime-version :date:message-id:from:to:cc:subject:date:message-id:reply-to; bh=buMAg0LS8akaLYVn1mf1luZlef5FqtF+8iT745eiTPQ=; b=M4Zjy8lA++k1LH1tBehoWiNrSnil4lkDgJKQU5rzB6HtSx3zjRt8ev/RejGfXRzNHd U25PHBDigg7CWp44YPTJvjaDvWbUPJ5VOv/yGnjxC0+xatoTNWeY7cO5OXBGYrWfJXz/ E9TqiGjz20V04z/W/oKVwdnrHlyTsWOH7TXEN4IIdmw1fz369RLeMduJ6gvAJUybS6Vk ywnpmHleg0NGxlPMklRNFJ81grAsJ2okJirihyNP0KcvgT3fvgPx1WkyzNDlE/lGV3jV fWS3r/L3spfbInoWnU66zHJYNhJMC0arFX9luTJBlAEwVR94fi8TszSB35XKvbAzUm95 dnBA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1716476987; x=1717081787; h=content-transfer-encoding:in-reply-to:autocrypt:from :content-language:references:cc:to:subject:user-agent:mime-version :date:message-id:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=buMAg0LS8akaLYVn1mf1luZlef5FqtF+8iT745eiTPQ=; b=sOUYi4XJHDLM4sOVpPHrU8NNadprsJ9rjcq3aXu0+mDVhGK02nWs1QsaqqDcBfIRSL HPBqQlQcu5AUuVv7Qn23+CkoYCNGv5yCVm/KmbqW50PU+r4pSqpRlKM93LjcbEQtArwM qtbd257fM27AF0HFpuaUQ6C7q2rqPpLyV9qSyX8H/pmyzwE5doxwvscOjUVZ3ejW10bv 4yggBIxylV3bJv0MtU963Y8p3+IUvfCpVdxmKR7BRy1Es3UbKJG8CekiElHTGrmGYebH fgeUuP1T1G5JnpBo+N5t3r2o1BDjShpzInHA0w0k83LgpuWVx29YM7asAjVLqB/51ggF mmbw== X-Forwarded-Encrypted: i=1; AJvYcCWcjLVC3wTIEvOihKzX4cc4yNZ19fR9KbpcdSj96RVcCYY8UPXD0ws183rQln+bTrV2E8CVKicdPA6fxgILR1AzlSnXHfK5pllaGf05gkY= X-Gm-Message-State: AOJu0Yzbtfcpx5daRCWIDVUPxiEzDJCPynBz60Za6aPP7khisJdR0vyl WEP97I6hs+mO3fWxvvwFZIGyqJUFCNdOXj+GYr4AMDCqLvhS8MccskIoQl3bsA== X-Google-Smtp-Source: AGHT+IFJHdPcenIMGjRAmc4re1PrzhAy95N3NTcdJzLheVYPZq5oaJ6ZqnQn+4w1/sliI+3BAX498Q== X-Received: by 2002:a17:907:26cb:b0:a59:f30e:fecd with SMTP id a640c23a62f3a-a622807a844mr454892266b.2.1716476986989; Thu, 23 May 2024 08:09:46 -0700 (PDT) Message-ID: <1def14d9-f98e-432e-b5bb-db6cd64676a2@suse.com> Date: Thu, 23 May 2024 17:09:45 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/7] x86/xstate: Fix initialisation of XSS cache To: Andrew Cooper Cc: =?UTF-8?Q?Roger_Pau_Monn=C3=A9?= , Xen-devel References: <20240523111627.28896-1-andrew.cooper3@citrix.com> <20240523111627.28896-2-andrew.cooper3@citrix.com> Content-Language: en-US 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: <20240523111627.28896-2-andrew.cooper3@citrix.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 23.05.2024 13:16, Andrew Cooper wrote: > The clobbering of this_cpu(xcr0) and this_cpu(xss) to architecturally invalid > values is to force the subsequent set_xcr0() and set_msr_xss() to reload the > hardware register. > > While XCR0 is reloaded in xstate_init(), MSR_XSS isn't. This causes > get_msr_xss() to return the invalid value, and logic of the form: > > old = get_msr_xss(); > set_msr_xss(new); > ... > set_msr_xss(old); > > to try and restore the architecturally invalid value. > > The architecturally invalid value must be purged from the cache, meaning the > hardware register must be written at least once. This in turn highlights that > the invalid value must only be used in the case that the hardware register is > available. > > Fixes: f7f4a523927f ("x86/xstate: reset cached register values on resume") > Signed-off-by: Andrew Cooper Reviewed-by: Jan Beulich However, I view it as pretty unfair that now I will need to re-base https://lists.xen.org/archives/html/xen-devel/2021-04/msg01336.html over ... > --- a/xen/arch/x86/xstate.c > +++ b/xen/arch/x86/xstate.c > @@ -641,13 +641,6 @@ void xstate_init(struct cpuinfo_x86 *c) > return; > } > > - /* > - * Zap the cached values to make set_xcr0() and set_msr_xss() really > - * write it. > - */ > - this_cpu(xcr0) = 0; > - this_cpu(xss) = ~0; > - > cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx); > feature_mask = (((u64)edx << 32) | eax) & XCNTXT_MASK; > BUG_ON(!valid_xcr0(feature_mask)); > @@ -657,8 +650,19 @@ void xstate_init(struct cpuinfo_x86 *c) > * Set CR4_OSXSAVE and run "cpuid" to get xsave_cntxt_size. > */ > set_in_cr4(X86_CR4_OSXSAVE); > + > + /* > + * Zap the cached values to make set_xcr0() and set_msr_xss() really write > + * the hardware register. > + */ > + this_cpu(xcr0) = 0; > if ( !set_xcr0(feature_mask) ) > BUG(); > + if ( cpu_has_xsaves ) > + { > + this_cpu(xss) = ~0; > + set_msr_xss(0); > + } ... this change, kind of breaking again your nice arrangement. Seeing for how long that change has been pending, it _really_ should have gone in ahead of this one, with you then sorting how you'd like things to be arranged in the combined result, rather than me re-posting and then either again not getting any feedback for years, or you disliking what I've done. Oh well ... Jan