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AJvYcCXxuHAVZohcW6EYAoz2hLxYsIPAZqRBn0rlebnBGG2A+a6hOr9nWFrvGPbBeBsq94Po8s99qpD2gPA=@lists.xenproject.org X-Gm-Message-State: AOJu0Yx1tgKirRV5YnisVB365bzBRyZv/9+5ecRdW/oyv8QhBYHl7f/s BBiBblULvYG4MG10DbZOXd54XdAAQDhc8eqPSBJUL8AeUrzCaPB8KKOOhP+z3w== X-Google-Smtp-Source: AGHT+IE95yimQ66gwnbKjNW7UTbSk2zlDHDbnJPw0vLYIxLqieqHGE27DGFyY6BIUJi3J6D52175pg== X-Received: by 2002:a17:907:72cd:b0:a9a:ca:4436 with SMTP id a640c23a62f3a-a9e40bd0b7fmr116195766b.13.1730271069339; Tue, 29 Oct 2024 23:51:09 -0700 (PDT) Message-ID: <14173e8a-ec20-455a-87bf-ae6d3d9a9051@suse.com> Date: Wed, 30 Oct 2024 07:51:08 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] x86/cpu-policy: Extend the guest max policy max leaf/subleaves To: Andrew Cooper Cc: =?UTF-8?Q?Roger_Pau_Monn=C3=A9?= , Alejandro Vallejo , Xen-devel References: <20241029175505.2698661-1-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: <20241029175505.2698661-1-andrew.cooper3@citrix.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 29.10.2024 18:55, Andrew Cooper wrote: > We already have one migration case opencoded (feat.max_subleaf). A more > recent discovery is that we advertise x2APIC to guests without ensuring that > we provide max_leaf >= 0xb. > > In general, any leaf known to Xen can be safely configured by the toolstack if > it doesn't violate other constraints. > > Therefore, introduce guest_common_{max,default}_leaves() to generalise the > special case we currently have for feat.max_subleaf, in preparation to be able > to provide x2APIC topology in leaf 0xb even on older hardware. > > Signed-off-by: Andrew Cooper Reviewed-by: Jan Beulich I'll have to update the AMX logic accordingly (maybe also the AVX10 one). I'd like to point out that this highlights a naming anomaly in x86_cpu_policies_are_compatible(): update_domain_cpu_policy() passes in the respective max policy as first argument. Imo the first parameter of the function would better be named "max" there. > --- a/xen/arch/x86/cpu-policy.c > +++ b/xen/arch/x86/cpu-policy.c > @@ -391,6 +391,27 @@ static void __init calculate_host_policy(void) > p->platform_info.cpuid_faulting = cpu_has_cpuid_faulting; > } > > +/* > + * Guest max policies can have any max leaf/subleaf within bounds. > + * > + * - Some incoming VMs have a larger-than-necessary feat max_subleaf. > + * - Some VMs we'd like to synthesise leaves not present on the host. > + */ > +static void __init guest_common_max_leaves(struct cpu_policy *p) > +{ > + p->basic.max_leaf = ARRAY_SIZE(p->basic.raw) - 1; > + p->feat.max_subleaf = ARRAY_SIZE(p->feat.raw) - 1; > + p->extd.max_leaf = 0x80000000U + ARRAY_SIZE(p->extd.raw) - 1; > +} > + > +/* Guest default policies inherit the host max leaf/subleaf settings. */ > +static void __init guest_common_default_leaves(struct cpu_policy *p) > +{ > + p->basic.max_leaf = host_cpu_policy.basic.max_leaf; > + p->feat.max_subleaf = host_cpu_policy.feat.max_subleaf; > + p->extd.max_leaf = host_cpu_policy.extd.max_leaf; > +} Which sadly still leaves open how to suitably shrink the max values, when they're larger than necessary (for the guest). Jan