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Mon, 22 Apr 2024 06:59:49 -0700 (PDT) Message-ID: <5df4d9d1-bec3-4798-9664-a4c75817a766@suse.com> Date: Mon, 22 Apr 2024 15:59:48 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/2] x86/spec: adjust logic to logic that elides lfence Content-Language: en-US To: =?UTF-8?Q?Roger_Pau_Monn=C3=A9?= , Andrew Cooper Cc: xen-devel@lists.xenproject.org References: <20240418155208.7771-1-roger.pau@citrix.com> <20240418155208.7771-3-roger.pau@citrix.com> <26b9cbda-4f9b-4ddf-ab27-643e6f78b076@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 22.04.2024 15:35, Roger Pau Monné wrote: > On Fri, Apr 19, 2024 at 08:25:00AM +0200, Jan Beulich wrote: >> On 18.04.2024 17:52, Roger Pau Monne wrote: >>> --- a/xen/arch/x86/include/asm/cpufeature.h >>> +++ b/xen/arch/x86/include/asm/cpufeature.h >>> @@ -235,9 +235,6 @@ static inline bool boot_cpu_has(unsigned int feat) >>> #define cpu_bug_fpu_ptrs boot_cpu_has(X86_BUG_FPU_PTRS) >>> #define cpu_bug_null_seg boot_cpu_has(X86_BUG_NULL_SEG) >>> >>> -#define cpu_has_bhb_seq (boot_cpu_has(X86_SPEC_BHB_TSX) || \ >>> - boot_cpu_has(X86_SPEC_BHB_LOOPS)) >> >> Might be worth also mentioning in the description that this construct was >> lacking use of X86_SPEC_BHB_LOOPS_LONG (might even warrant a 2nd Fixes: >> tag). > > Heh, no, X86_SPEC_BHB_LOOPS_LONG is added in addition to > X86_SPEC_BHB_LOOPS. When using long loops we have both > X86_SPEC_BHB_LOOPS and X86_SPEC_BHB_LOOPS_LONG set (I know it's > confusing, I was also confused the first time and asked Andrew the > same question). See the fallthrough in bhi_calculations(). Oh, I see. Andrew: This is a very good example of the separating blank line being misleading when fall-through is intended. Jan