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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: <20260420174605.706329-1-andrew.cooper3@citrix.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-purgate-ID: tlsNG-c201ff/1776753546-E1BA4443-50D61DF6/0/0 X-purgate-type: clean X-purgate-size: 1984 On 20.04.2026 19:46, Andrew Cooper wrote: > The encoded MUL is 64 bits, so writes %rdx too. At a minimum, this needs > expressing as a clobber. I'm embarrassed of missing this. > Also fix a logical disconnect between 'overflow' being the carry flag not the > overflow flag. CF and OF are always the same for MUL instructions, so use the > flag which matches the variable name. I don't mind this too much, but the use of CF was deliberate: Imo OF is relevant to signed arithmetic only, whereas CF is the flag to use with unsigned operations. > Fixes: d5c70a51bfbe ("x86/APIC: handle overflow in TMICT calculation") > Signed-off-by: Andrew Cooper Reviewed-by: Jan Beulich > I've kept this form because it produces best code generation for GCCs which > support flag outputs. > > An alternative would be to capture product_hi and check the nonzero-ness, as > that's how OF/CF are produced in hardware, which would be better code > generation on very old GCCs. We could fit both, by further widening the use of ASM_FLAG_OUT(). > --- a/xen/arch/x86/apic.c > +++ b/xen/arch/x86/apic.c > @@ -1317,9 +1317,10 @@ int reprogram_timer(s_time_t timeout) > > apic_tmict = UINT32_MAX; > asm ( "mul %[expire]\n\t" > - ASM_FLAG_OUT(, "setc %[cf]") > - : "=a" (product), [cf] ASM_FLAG_OUT("=@ccc", "=qm") (overflow) > - : "0" ((unsigned long)bus_scale), [expire] "r" (expire) ); > + ASM_FLAG_OUT(, "seto %[of]") > + : "=a" (product), [of] ASM_FLAG_OUT("=@cco", "=qm") (overflow) Noticing only now - for the non-flag-output case this should be "=&a". With > + : "0" ((unsigned long)bus_scale), [expire] "r" (expire) ... %rax also being an input, there's no risk of the compiler using the register for the other input, but still. Would you mind making that adjustment as well, while at it? Jan