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/arm/include/asm/xen/page.h | 23 +++++++++++++++++++++-- 1 file changed, 21 insertions(+), 2 deletions(-) (limited to 'arch/arm/include/asm/xen/page.h') diff --git a/arch/arm/include/asm/xen/page.h b/arch/arm/include/asm/xen/page.h index 98b1084f8282..5f76a9e7ef1b 100644 --- a/arch/arm/include/asm/xen/page.h +++ b/arch/arm/include/asm/xen/page.h @@ -52,7 +52,26 @@ static inline unsigned long mfn_to_pfn(unsigned long mfn) return mfn; } -#define mfn_to_local_pfn(mfn) mfn_to_pfn(mfn) +/* Pseudo-physical <-> BUS conversion */ +static inline unsigned long pfn_to_bfn(unsigned long pfn) +{ + unsigned long mfn; + + if (phys_to_mach.rb_node != NULL) { + mfn = __pfn_to_mfn(pfn); + if (mfn != INVALID_P2M_ENTRY) + return mfn; + } + + return pfn; +} + +static inline unsigned long bfn_to_pfn(unsigned long bfn) +{ + return bfn; +} + +#define bfn_to_local_pfn(bfn) bfn_to_pfn(bfn) /* VIRT <-> MACHINE conversion */ #define virt_to_mfn(v) (pfn_to_mfn(virt_to_pfn(v))) @@ -96,7 +115,7 @@ static inline bool set_phys_to_machine(unsigned long pfn, unsigned long mfn) bool xen_arch_need_swiotlb(struct device *dev, unsigned long pfn, - unsigned long mfn); + unsigned long bfn); unsigned long xen_get_swiotlb_free_pages(unsigned int order); #endif /* _ASM_ARM_XEN_PAGE_H */ -- cgit v1.2.3 From 5192b35de47e47a0f736fe30da199f32030680e7 Mon Sep 17 00:00:00 2001 From: Julien Grall Date: Fri, 7 Aug 2015 17:34:36 +0100 Subject: arm/xen: implement correctly pfn_to_mfn After the commit introducing convertion between DMA and guest addresses, all the callers of pfn_to_mfn are expecting to get a GFN (Guest Frame Number). On ARM, all the guests are auto-translated so the GFN is equal to the Linux PFN (Pseudo-physical Frame Number). The current implementation may return an MFN if the caller is passing a PFN associated to a mapped foreign grant. In pratice, I haven't seen the problem on running guest but we should fix it for the sake of correctness. Correct the implementation by always returning the pfn passed in parameter. A follow-up patch will take care to rename pfn_to_mfn to a suitable name. Signed-off-by: Julien Grall Reviewed-by: Stefano Stabellini Signed-off-by: David Vrabel --- arch/arm/include/asm/xen/page.h | 8 -------- 1 file changed, 8 deletions(-) (limited to 'arch/arm/include/asm/xen/page.h') diff --git a/arch/arm/include/asm/xen/page.h b/arch/arm/include/asm/xen/page.h index 5f76a9e7ef1b..911d62b4df26 100644 --- a/arch/arm/include/asm/xen/page.h +++ b/arch/arm/include/asm/xen/page.h @@ -36,14 +36,6 @@ extern struct rb_root phys_to_mach; static inline unsigned long pfn_to_mfn(unsigned long pfn) { - unsigned long mfn; - - if (phys_to_mach.rb_node != NULL) { - mfn = __pfn_to_mfn(pfn); - if (mfn != INVALID_P2M_ENTRY) - return mfn; - } - return pfn; } -- 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/arm/include/asm/xen/page.h | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) (limited to 'arch/arm/include/asm/xen/page.h') diff --git a/arch/arm/include/asm/xen/page.h b/arch/arm/include/asm/xen/page.h index 911d62b4df26..127956353b00 100644 --- a/arch/arm/include/asm/xen/page.h +++ b/arch/arm/include/asm/xen/page.h @@ -34,14 +34,15 @@ typedef struct xpaddr { unsigned long __pfn_to_mfn(unsigned long pfn); extern struct rb_root phys_to_mach; -static inline unsigned long pfn_to_mfn(unsigned long pfn) +/* Pseudo-physical <-> Guest conversion */ +static inline unsigned long pfn_to_gfn(unsigned long pfn) { return pfn; } -static inline unsigned long mfn_to_pfn(unsigned long mfn) +static inline unsigned long gfn_to_pfn(unsigned long gfn) { - return mfn; + return gfn; } /* Pseudo-physical <-> BUS conversion */ @@ -65,9 +66,9 @@ static inline unsigned long bfn_to_pfn(unsigned long bfn) #define bfn_to_local_pfn(bfn) bfn_to_pfn(bfn) -/* VIRT <-> MACHINE conversion */ -#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(m) (__va(gfn_to_pfn(m) << PAGE_SHIFT)) /* Only used in PV code. But ARM guests are always HVM. */ static inline xmaddr_t arbitrary_virt_to_machine(void *vaddr) -- cgit v1.2.3