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Wed, 18 Dec 2019 07:01:17 +0000 (UTC) Received: from thuth.remote.csb (ovpn-116-150.ams2.redhat.com [10.36.116.150]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 0F4097D8FC; Wed, 18 Dec 2019 07:01:13 +0000 (UTC) Subject: Re: [PATCH 2/7] tcg: Remove softmmu code_gen_buffer fixed address To: Richard Henderson , qemu-devel@nongnu.org References: <20191218031920.6414-1-richard.henderson@linaro.org> <20191218031920.6414-3-richard.henderson@linaro.org> From: Thomas Huth Openpgp: preference=signencrypt Message-ID: Date: Wed, 18 Dec 2019 08:01:12 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <20191218031920.6414-3-richard.henderson@linaro.org> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-MC-Unique: Hh_R525kOpqx0rPYvmqCqw-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.120 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: berrange@redhat.com, i@maskray.me, philmd@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 18/12/2019 04.19, Richard Henderson wrote: > The commentary talks about "in concert with the addresses > assigned in the relevant linker script", except there is no > linker script for softmmu, nor has there been for some time. > > (Do not confuse the user-only linker script editing that was > removed in the previous patch, because user-only does not > use this code_gen_buffer allocation method.) > > Signed-off-by: Richard Henderson > --- > accel/tcg/translate-all.c | 37 +++++-------------------------------- > 1 file changed, 5 insertions(+), 32 deletions(-) > > diff --git a/accel/tcg/translate-all.c b/accel/tcg/translate-all.c > index 9f48da9472..88468a1c08 100644 > --- a/accel/tcg/translate-all.c > +++ b/accel/tcg/translate-all.c > @@ -1032,47 +1032,20 @@ static inline void *alloc_code_gen_buffer(void) > { > int prot = PROT_WRITE | PROT_READ | PROT_EXEC; > int flags = MAP_PRIVATE | MAP_ANONYMOUS; > - uintptr_t start = 0; > size_t size = tcg_ctx->code_gen_buffer_size; > void *buf; > > - /* Constrain the position of the buffer based on the host cpu. > - Note that these addresses are chosen in concert with the > - addresses assigned in the relevant linker script file. */ > -# if defined(__PIE__) || defined(__PIC__) > - /* Don't bother setting a preferred location if we're building > - a position-independent executable. We're more likely to get > - an address near the main executable if we let the kernel > - choose the address. */ > -# elif defined(__x86_64__) && defined(MAP_32BIT) > - /* Force the memory down into low memory with the executable. > - Leave the choice of exact location with the kernel. */ > - flags |= MAP_32BIT; > - /* Cannot expect to map more than 800MB in low memory. */ > - if (size > 800u * 1024 * 1024) { > - tcg_ctx->code_gen_buffer_size = size = 800u * 1024 * 1024; > - } > -# elif defined(__sparc__) > - start = 0x40000000ul; > -# elif defined(__s390x__) > - start = 0x90000000ul; > -# elif defined(__mips__) > -# if _MIPS_SIM == _ABI64 > - start = 0x128000000ul; > -# else > - start = 0x08000000ul; > -# endif > -# endif > - > - buf = mmap((void *)start, size, prot, flags, -1, 0); > + buf = mmap(NULL, size, prot, flags, -1, 0); > if (buf == MAP_FAILED) { > return NULL; > } > > #ifdef __mips__ > if (cross_256mb(buf, size)) { > - /* Try again, with the original still mapped, to avoid re-acquiring > - that 256mb crossing. This time don't specify an address. */ > + /* > + * Try again, with the original still mapped, to avoid re-acquiring > + * the same 256mb crossing. > + */ > size_t size2; > void *buf2 = mmap(NULL, size, prot, flags, -1, 0); > switch ((int)(buf2 != MAP_FAILED)) { > Reviewed-by: Thomas Huth