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Date: Mon, 28 Mar 2022 10:59:24 +0000 From: Christophe Leroy <christophe.leroy@...roup.eu> To: Michael Ellerman <mpe@...erman.id.au>, Kefeng Wang <wangkefeng.wang@...wei.com>, "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org> CC: "npiggin@...il.com" <npiggin@...il.com>, "songyuanzheng@...wei.com" <songyuanzheng@...wei.com> Subject: Re: [PATCH v4 1/2] Revert "powerpc: Set max_mapnr correctly" Le 28/03/2022 à 12:37, Michael Ellerman a écrit : > Kefeng Wang <wangkefeng.wang@...wei.com> writes: >> Hi maintainers, >> >> I saw the patches has been reviewed[1], could they be merged? > > Maybe I'm just misreading the change log, but it seems wrong that we > need to add extra checks. pfn_valid() shouldn't return true for vmalloc > addresses in the first place, shouldn't we fix that instead? Who knows > what else that might be broken because of that. > pfn_valid() doesn't take an address but a PFN If you have 1Gbyte of memory you have 256k PFNs. In a generic config the kernel will map 768 Mbytes of mémory (From 0xc0000000 to 0xe0000000) and will use 0xf0000000-0xffffffff for everything else including vmalloc. If you take a page above that 768 Mbytes limit, and tries to linarly convert it's PFN to a va, you'll hip vmalloc space. Anyway that PFN is valid. So the check really needs to be done in virt_addr_valid(). There is another thing however that would be worth fixing (in another patch): that's the virt_to_pfn() in PPC64: #define virt_to_pfn(kaddr) (__pa(kaddr) >> PAGE_SHIFT) #define __pa(x) \ ({ \ VIRTUAL_BUG_ON((unsigned long)(x) < PAGE_OFFSET); \ (unsigned long)(x) & 0x0fffffffffffffffUL; \ }) So 0xc000000000000000 and 0xd000000000000000 have the same PFN. That's wrong. Christophe
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