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[37.24.206.209]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a89891968a3sm819605866b.142.2024.09.04.06.27.27 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 04 Sep 2024 06:27:28 -0700 (PDT) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: 6e8c41ca-6ac1-11ef-a0b3-8be0dac302b0 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=google; t=1725456448; x=1726061248; darn=lists.xenproject.org; h=content-transfer-encoding:in-reply-to:autocrypt:content-language :references:cc:to:from:subject:user-agent:mime-version:date :message-id:from:to:cc:subject:date:message-id:reply-to; bh=yp78HPLZHcPEMDsLsM1R4Jfv8UU1lMcs6c7lpFRwulA=; b=HwLhc7LgviDxCzUKsbVjuw1dr5cZ3Y3DvN9LvXx7h6z1t3EeYMbvrFyLAZptDeIz4I iLFGRobu5eV28tk/iu4GxO2C0cdRNMUnUFlZbeHOoJBMVYiXgI8GsEu+FOoWBNwLDfmZ 0xs1BLvBi/d9l78M5kGCvYFQJ8j0lLScfx62dAocbg+8vmtMxvnKzzV7ZqXAZuBI9CnM w6NlNujAICJ12NeZkGxRcibIqtJGR/hs9ycsvtYlEh2F+eXKXJAjgL574mpx1TxgvgU8 wHelZtPKrWSCbA3lndsc34zsnM+mYi7/mLi6rIfa4QFMJFVzUVhg8g1FWkuUHNdIhvTQ /KoQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1725456448; x=1726061248; h=content-transfer-encoding:in-reply-to:autocrypt:content-language :references:cc:to:from:subject:user-agent:mime-version:date :message-id:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=yp78HPLZHcPEMDsLsM1R4Jfv8UU1lMcs6c7lpFRwulA=; b=OXHSc8Hk+q/IBiiBhEcP/50mIP/4TtUWM3/0HuL69p0OfflaHDXfhE6jPEUUzUpwn0 kuAlD/nAuVxvCBnN5w7JKDnao9qtzVXRW/YXtZToKqCXoVnlhzxWDbNvX9LVMCeCajpH L1FZ0jklLCaUlqIpNY46MPuhUrM0y92bOR2i1G9TO3Jg+N8tk5KVDc/3nr49RqwdjCgj fxfKtS+IOwrikwA6G2gccUj4L2loNtmfYltfVyIPFXQ8qrMzlJHmmoEfzOqkTJgQoIpJ fW0SvBCxvb06H3xzWNAeml+8vASBi4THM0gA0Y5RMLUOgKg873HwVvsPXRRLmkEpHEKn +zyQ== X-Gm-Message-State: AOJu0Yx1K3Ekt6HiEWpYPnDQlFyAvNITjbW/R4ifzfCk3l6FHf1E7l5N +OcDaW4GfqpKkhlmew3hVixp+pEi2jUJjSyNJCjcTCkjhs058j5FW7TQtffr/N2IiE5vxJnvk8I = X-Google-Smtp-Source: AGHT+IGJDFc47MWj8OXx8n+le8xzZBSP7AtarY8vuRHUCUsZvG02uHr5q+kfFwMBISDnNkSW6UQZvw== X-Received: by 2002:a17:907:cc88:b0:a8a:5a72:a29f with SMTP id a640c23a62f3a-a8a5a72a500mr58705766b.17.1725456448231; Wed, 04 Sep 2024 06:27:28 -0700 (PDT) Message-ID: Date: Wed, 4 Sep 2024 15:27:26 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: [PATCH 1/5] x86/HVM: reduce recursion in linear_{read,write}() From: Jan Beulich To: "xen-devel@lists.xenproject.org" Cc: Andrew Cooper , =?utf-8?q?Roger_Pau_Monn?= =?utf-8?q?=C3=A9?= References: <31906cba-8646-4cf9-ab31-1d23654df8d1@suse.com> Content-Language: en-US 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: <31906cba-8646-4cf9-ab31-1d23654df8d1@suse.com> Let's make explicit what the compiler may or may not do on our behalf: The 2nd of the recursive invocations each can fall through rather than re-invoking the function. This will save us from adding yet another parameter (or more) to the function, just for the recursive invocations. Signed-off-by: Jan Beulich Reviewed-by: Andrew Cooper --- a/xen/arch/x86/hvm/emulate.c +++ b/xen/arch/x86/hvm/emulate.c @@ -1146,7 +1146,7 @@ static int linear_read(unsigned long add pagefault_info_t pfinfo; struct hvm_vcpu_io *hvio = ¤t->arch.hvm.hvm_io; unsigned int offset = addr & ~PAGE_MASK; - int rc = HVMTRANS_bad_gfn_to_mfn; + int rc; if ( offset + bytes > PAGE_SIZE ) { @@ -1154,12 +1154,16 @@ static int linear_read(unsigned long add /* Split the access at the page boundary. */ rc = linear_read(addr, part1, p_data, pfec, hvmemul_ctxt); - if ( rc == X86EMUL_OKAY ) - rc = linear_read(addr + part1, bytes - part1, p_data + part1, - pfec, hvmemul_ctxt); - return rc; + if ( rc != X86EMUL_OKAY ) + return rc; + + addr += part1; + bytes -= part1; + p_data += part1; } + rc = HVMTRANS_bad_gfn_to_mfn; + /* * If there is an MMIO cache entry for the access then we must be re-issuing * an access that was previously handled as MMIO. Thus it is imperative that @@ -1201,7 +1205,7 @@ static int linear_write(unsigned long ad pagefault_info_t pfinfo; struct hvm_vcpu_io *hvio = ¤t->arch.hvm.hvm_io; unsigned int offset = addr & ~PAGE_MASK; - int rc = HVMTRANS_bad_gfn_to_mfn; + int rc; if ( offset + bytes > PAGE_SIZE ) { @@ -1209,12 +1213,16 @@ static int linear_write(unsigned long ad /* Split the access at the page boundary. */ rc = linear_write(addr, part1, p_data, pfec, hvmemul_ctxt); - if ( rc == X86EMUL_OKAY ) - rc = linear_write(addr + part1, bytes - part1, p_data + part1, - pfec, hvmemul_ctxt); - return rc; + if ( rc != X86EMUL_OKAY ) + return rc; + + addr += part1; + bytes -= part1; + p_data += part1; } + rc = HVMTRANS_bad_gfn_to_mfn; + /* * If there is an MMIO cache entry for the access then we must be re-issuing * an access that was previously handled as MMIO. Thus it is imperative that