From 32e09870eedfb501a6cb5729d8c23f44f8a7cbdd Mon Sep 17 00:00:00 2001 From: Julien Grall Date: Fri, 7 Aug 2015 17:34:35 +0100 Subject: xen: Make clear that swiotlb and biomerge are dealing with DMA address The swiotlb is required when programming a DMA address on ARM when a device is not protected by an IOMMU. In this case, the DMA address should always be equal to the machine address. For DOM0 memory, Xen ensure it by have an identity mapping between the guest address and host address. However, when mapping a foreign grant reference, the 1:1 model doesn't work. For ARM guest, most of the callers of pfn_to_mfn expects to get a GFN (Guest Frame Number), i.e a PFN (Page Frame Number) from the Linux point of view given that all ARM guest are auto-translated. Even though the name pfn_to_mfn is misleading, we need to ensure that those caller get a GFN and not by mistake a MFN. In pratical, I haven't seen error related to this but we should fix it for the sake of correctness. In order to fix the implementation of pfn_to_mfn on ARM in a follow-up patch, we have to introduce new helpers to return the DMA from a PFN and the invert. On x86, the new helpers will be an alias of pfn_to_mfn and mfn_to_pfn. The helpers will be used in swiotlb and xen_biovec_phys_mergeable. This is necessary in the latter because we have to ensure that the biovec code will not try to merge a biovec using foreign page and another using Linux memory. Lastly, the helper mfn_to_local_pfn has been renamed to bfn_to_local_pfn given that the only usage was in swiotlb. Signed-off-by: Julien Grall Reviewed-by: Stefano Stabellini Signed-off-by: David Vrabel --- arch/x86/include/asm/xen/page.h | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) (limited to 'arch/x86/include/asm/xen/page.h') diff --git a/arch/x86/include/asm/xen/page.h b/arch/x86/include/asm/xen/page.h index a3804fbe1f36..724bffbde54d 100644 --- a/arch/x86/include/asm/xen/page.h +++ b/arch/x86/include/asm/xen/page.h @@ -176,6 +176,10 @@ static inline xpaddr_t machine_to_phys(xmaddr_t machine) return XPADDR(PFN_PHYS(mfn_to_pfn(PFN_DOWN(machine.maddr))) | offset); } +/* Pseudo-physical <-> Bus conversion */ +#define pfn_to_bfn(pfn) pfn_to_mfn(pfn) +#define bfn_to_pfn(bfn) mfn_to_pfn(bfn) + /* * We detect special mappings in one of two ways: * 1. If the MFN is an I/O page then Xen will set the m2p entry @@ -196,7 +200,7 @@ static inline xpaddr_t machine_to_phys(xmaddr_t machine) * require. In all the cases we care about, the FOREIGN_FRAME bit is * masked (e.g., pfn_to_mfn()) so behaviour there is correct. */ -static inline unsigned long mfn_to_local_pfn(unsigned long mfn) +static inline unsigned long bfn_to_local_pfn(unsigned long mfn) { unsigned long pfn; @@ -262,7 +266,7 @@ void make_lowmem_page_readwrite(void *vaddr); static inline bool xen_arch_need_swiotlb(struct device *dev, unsigned long pfn, - unsigned long mfn) + unsigned long bfn) { return false; } -- cgit v1.2.3 From 0df4f266b3af90442bbeb5e685a84a80745beba0 Mon Sep 17 00:00:00 2001 From: Julien Grall Date: Fri, 7 Aug 2015 17:34:37 +0100 Subject: xen: Use correctly the Xen memory terminologies Based on include/xen/mm.h [1], Linux is mistakenly using MFN when GFN is meant, I suspect this is because the first support for Xen was for PV. This resulted in some misimplementation of helpers on ARM and confused developers about the expected behavior. For instance, with pfn_to_mfn, we expect to get an MFN based on the name. Although, if we look at the implementation on x86, it's returning a GFN. For clarity and avoid new confusion, replace any reference to mfn with gfn in any helpers used by PV drivers. The x86 code will still keep some reference of pfn_to_mfn which may be used by all kind of guests No changes as been made in the hypercall field, even though they may be invalid, in order to keep the same as the defintion in xen repo. Note that page_to_mfn has been renamed to xen_page_to_gfn to avoid a name to close to the KVM function gfn_to_page. Take also the opportunity to simplify simple construction such as pfn_to_mfn(page_to_pfn(page)) into xen_page_to_gfn. More complex clean up will come in follow-up patches. [1] http://xenbits.xen.org/gitweb/?p=xen.git;a=commitdiff;h=e758ed14f390342513405dd766e874934573e6cb Signed-off-by: Julien Grall Reviewed-by: Stefano Stabellini Acked-by: Dmitry Torokhov Acked-by: Wei Liu Signed-off-by: David Vrabel --- arch/x86/include/asm/xen/page.h | 35 +++++++++++++++++++++++++++++++++-- 1 file changed, 33 insertions(+), 2 deletions(-) (limited to 'arch/x86/include/asm/xen/page.h') diff --git a/arch/x86/include/asm/xen/page.h b/arch/x86/include/asm/xen/page.h index 724bffbde54d..0679e11d2cf7 100644 --- a/arch/x86/include/asm/xen/page.h +++ b/arch/x86/include/asm/xen/page.h @@ -101,6 +101,11 @@ static inline unsigned long pfn_to_mfn(unsigned long pfn) { unsigned long mfn; + /* + * Some x86 code are still using pfn_to_mfn instead of + * pfn_to_mfn. This will have to be removed when we figured + * out which call. + */ if (xen_feature(XENFEAT_auto_translated_physmap)) return pfn; @@ -147,6 +152,11 @@ static inline unsigned long mfn_to_pfn(unsigned long mfn) { unsigned long pfn; + /* + * Some x86 code are still using mfn_to_pfn instead of + * gfn_to_pfn. This will have to be removed when we figure + * out which call. + */ if (xen_feature(XENFEAT_auto_translated_physmap)) return mfn; @@ -176,9 +186,26 @@ static inline xpaddr_t machine_to_phys(xmaddr_t machine) return XPADDR(PFN_PHYS(mfn_to_pfn(PFN_DOWN(machine.maddr))) | offset); } +/* Pseudo-physical <-> Guest conversion */ +static inline unsigned long pfn_to_gfn(unsigned long pfn) +{ + if (xen_feature(XENFEAT_auto_translated_physmap)) + return pfn; + else + return pfn_to_mfn(pfn); +} + +static inline unsigned long gfn_to_pfn(unsigned long gfn) +{ + if (xen_feature(XENFEAT_auto_translated_physmap)) + return gfn; + else + return mfn_to_pfn(gfn); +} + /* Pseudo-physical <-> Bus conversion */ -#define pfn_to_bfn(pfn) pfn_to_mfn(pfn) -#define bfn_to_pfn(bfn) mfn_to_pfn(bfn) +#define pfn_to_bfn(pfn) pfn_to_gfn(pfn) +#define bfn_to_pfn(bfn) gfn_to_pfn(bfn) /* * We detect special mappings in one of two ways: @@ -219,6 +246,10 @@ static inline unsigned long bfn_to_local_pfn(unsigned long mfn) #define virt_to_mfn(v) (pfn_to_mfn(virt_to_pfn(v))) #define mfn_to_virt(m) (__va(mfn_to_pfn(m) << PAGE_SHIFT)) +/* VIRT <-> GUEST conversion */ +#define virt_to_gfn(v) (pfn_to_gfn(virt_to_pfn(v))) +#define gfn_to_virt(g) (__va(gfn_to_pfn(g) << PAGE_SHIFT)) + static inline unsigned long pte_mfn(pte_t pte) { return (pte.pte & PTE_PFN_MASK) >> PAGE_SHIFT; -- cgit v1.2.3