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AJvYcCXzFl3RZVFh09IQe+JrX5inWuBvE+efNtWmgbNvTsUXh+7zp8hdOoxyd0RTITVBuBR7AhIP5f5E8AY=@lists.xenproject.org X-Gm-Message-State: AOJu0YwHUlAnLox5jcn9V3D33sCx/PcbtbIqKfaDp+bZ5fkCBeG5p+50 hfeD2zIHlp87Uxqn3xkDUq2yOXwPosATbqUIRqzXkxsc9aOB/0aUBAzUQ5wYjw== X-Google-Smtp-Source: AGHT+IHqDPRLkrFtfmKFzwgm+oJLPS40eFOB5dWMD7VHvGhGdqBaRh8v9jxpC71Y4eMRSL6pDWrKjA== X-Received: by 2002:a05:600c:3b93:b0:431:562a:54be with SMTP id 5b1f17b1804b1-432da77c15amr18800125e9.9.1731582670742; Thu, 14 Nov 2024 03:11:10 -0800 (PST) Message-ID: Date: Thu, 14 Nov 2024 12:11:09 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/3] x86/ucode: Remove the collect_cpu_info() call from parse_blob() To: Andrew Cooper Cc: =?UTF-8?Q?Roger_Pau_Monn=C3=A9?= , Xen-devel References: <20241112211915.1473121-1-andrew.cooper3@citrix.com> <20241112211915.1473121-2-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: <20241112211915.1473121-2-andrew.cooper3@citrix.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 12.11.2024 22:19, Andrew Cooper wrote: > With the tangle of logic starting to come under control, it is now plain to > see that parse_blob()'s side effect of re-gathering the signature/revision is > pointless. > > The cpu_request_microcode() hooks need the signature only. The BSP gathers > this in early_microcode_init(), the APs and S3 in microcode_update_cpu(). That's microcode_update_one() after 502478bc1d9d if I'm not mistaken. In the course of determining that I'm afraid I also found the first sentence of this paragraph rather misleading than helpful: While it is true what is being said, in both cases it is collect_cpu_info() that is being invoked, retrieving both signature and revision. IOW logic needing the signature only doesn't really matter here (and the sentence made me hunt for cases where we would read just the signature, aiming at verifying that leaving the revision field unset would indeed not be a problem). > For > good measure, the apply_microcode() hooks also keep the revision correct as > load attempts are made. > > This finally gets us down to a single call per CPU on boot / S3 resume, and no > calls during late-load hypercalls. > > No functional change. > > Signed-off-by: Andrew Cooper Preferably with the problematic sentence dropped or clarified: Reviewed-by: Jan Beulich Jan