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Wed, 28 Jul 2021 09:44:17 -0700 (PDT) From: Oleksandr Tyshchenko To: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Cc: Oleksandr Tyshchenko , Catalin Marinas , Will Deacon , Andrey Konovalov , Ard Biesheuvel , Vincenzo Frascino , Joey Gouly , Sami Tolvanen , Mark Rutland , Juergen Gross , Julien Grall , Wei Chen , Stefano Stabellini Subject: [RFC PATCH 1/2] arm64: mm: Make virt_addr_valid to check for pfn_valid again Date: Wed, 28 Jul 2021 19:44:15 +0300 Message-Id: <1627490656-1267-1-git-send-email-olekstysh@gmail.com> X-Mailer: git-send-email 2.7.4 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210728_094420_819342_DF9773D2 X-CRM114-Status: GOOD ( 19.43 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org From: Oleksandr Tyshchenko The problem is that Arm's implementation of virt_addr_valid() leads to memblock_is_map_memory() check, which will fail for ZONE_DEVICE based addresses. But, the pfn_valid() check in turn is able to cope with ZONE_DEVICE based memory. You can find a good explanation of that problem at: https://lore.kernel.org/lkml/1614921898-4099-2-git-send-email-anshuman.khandual@arm.com Signed-off-by: Oleksandr Tyshchenko --- I am not quite sure whether it is a "correct" place and the change itself, I just partially restored a behaviour before: https://lore.kernel.org/lkml/20210511100550.28178-4-rppt@kernel.org So, the target of this patch is to get a feedback how to resolve this properly if, of course, this really needs to be resolved (I might miss important bits here). It is worth mentioning that patch doesn't fix the current code base (if I am not mistaken, no one calls virt_addr_valid() on Arm64 for ZONE_DEVICE based addresses at the moment, so it seems that nothing is broken), the fix is intended for the subsequent patch in this series that will try to enable Xen's "unpopulated-alloc" usage on Arm (it was enabled on x86 so far). Please see: [RFC PATCH 2/2] xen/unpopulated-alloc: Query hypervisor to provide unallocated space The subsequent patch will enable the code where virt_addr_valid() is used in drivers/xen/unpopulated-alloc.c:fill_list() to check that a virtual address returned by memremap_pages() is valid. --- arch/arm64/include/asm/memory.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h index 824a365..1a35a44 100644 --- a/arch/arm64/include/asm/memory.h +++ b/arch/arm64/include/asm/memory.h @@ -351,7 +351,7 @@ static inline void *phys_to_virt(phys_addr_t x) #define virt_addr_valid(addr) ({ \ __typeof__(addr) __addr = __tag_reset(addr); \ - __is_lm_address(__addr) && pfn_is_map_memory(virt_to_pfn(__addr)); \ + __is_lm_address(__addr) && pfn_valid(virt_to_pfn(__addr)); \ }) void dump_mem_limit(void);