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Thu, 23 Jan 2025 01:20:14 -0800 (PST) Message-ID: <600c8bee-a6fd-41df-82bf-60ec15fec42c@suse.com> Date: Thu, 23 Jan 2025 10:20:13 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 5/5] x86/HVM: drop redundant access splitting To: =?UTF-8?Q?Roger_Pau_Monn=C3=A9?= Cc: "xen-devel@lists.xenproject.org" , Andrew Cooper References: <3294f629-f91f-4b5d-9eb0-40a34aa2ec3e@suse.com> <7d73f0c5-3d16-4cf3-b8de-e45f539e8916@suse.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: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 23.01.2025 10:01, Roger Pau MonnĂ© wrote: > On Tue, Oct 01, 2024 at 10:50:25AM +0200, Jan Beulich wrote: >> --- a/xen/arch/x86/hvm/emulate.c >> +++ b/xen/arch/x86/hvm/emulate.c >> @@ -1084,7 +1084,7 @@ static int hvmemul_linear_mmio_access( >> { >> struct hvm_vcpu_io *hvio = ¤t->arch.hvm.hvm_io; >> unsigned long offset = gla & ~PAGE_MASK; >> - unsigned int chunk, buffer_offset = gla - start; >> + unsigned int buffer_offset = gla - start; >> struct hvm_mmio_cache *cache = hvmemul_find_mmio_cache(hvio, start, dir, >> buffer_offset); >> paddr_t gpa; >> @@ -1094,13 +1094,17 @@ static int hvmemul_linear_mmio_access( >> if ( cache == NULL ) >> return X86EMUL_UNHANDLEABLE; >> >> - chunk = min_t(unsigned int, size, PAGE_SIZE - offset); >> + if ( size > PAGE_SIZE - offset ) > > FWIW, I find this easier to read as `size + offset > PAGE_SIZE` (which > is the same condition used in linear_{read,write}(). Hmm, yes, considering that "size" here is specifically what "bytes" is there, doing the change is okay. However, in general I prefer the way it was written above, for being more obviously safe against overflow (taking into account how "offset" is calculated). > Preferably with that adjusted: > > Acked-by: Roger Pau MonnĂ© Thanks. Jan