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The access >>> physical address will be original physical address + shared_gpa_boundary. >>> The shared_gpa_boundary in the AMD SEV SNP spec is called virtual top of >>> memory(vTOM). Memory addresses below vTOM are automatically treated as >>> private while memory above vTOM is treated as shared. >>> >>> Expose swiotlb_unencrypted_base for platforms to set unencrypted >>> memory base offset and platform calls swiotlb_update_mem_attributes() >>> to remap swiotlb mem to unencrypted address space. memremap() can >>> not be called in the early stage and so put remapping code into >>> swiotlb_update_mem_attributes(). Store remap address and use it to copy >>> data from/to swiotlb bounce buffer. >>> >>> Signed-off-by: Tianyu Lan >> >> This patch results in the following stack trace during a bare-metal boot >> on my EPYC system with SME active (e.g. mem_encrypt=on): >> >> [    0.123932] BUG: Bad page state in process swapper  pfn:108001 >> [    0.123942] page:(____ptrval____) refcount:0 mapcount:-128 >> mapping:0000000000000000 index:0x0 pfn:0x108001 >> [    0.123946] flags: 0x17ffffc0000000(node=0|zone=2|lastcpupid=0x1fffff) >> [    0.123952] raw: 0017ffffc0000000 ffff88904f2d5e80 ffff88904f2d5e80 >> 0000000000000000 >> [    0.123954] raw: 0000000000000000 0000000000000000 00000000ffffff7f >> 0000000000000000 >> [    0.123955] page dumped because: nonzero mapcount >> [    0.123957] Modules linked in: >> [    0.123961] CPU: 0 PID: 0 Comm: swapper Not tainted >> 5.16.0-rc3-sos-custom #2 >> [    0.123964] Hardware name: AMD Corporation >> [    0.123967] Call Trace: >> [    0.123971]  >> [    0.123975]  dump_stack_lvl+0x48/0x5e >> [    0.123985]  bad_page.cold+0x65/0x96 >> [    0.123990]  __free_pages_ok+0x3a8/0x410 >> [    0.123996]  memblock_free_all+0x171/0x1dc >> [    0.124005]  mem_init+0x1f/0x14b >> [    0.124011]  start_kernel+0x3b5/0x6a1 >> [    0.124016]  secondary_startup_64_no_verify+0xb0/0xbb >> [    0.124022]  >> >> I see ~40 of these traces, each for different pfns. >> >> Thanks, >> Tom > > Hi Tom: >       Thanks for your test. Could you help to test the following patch > and check whether it can fix the issue. The patch is mangled. Is the only difference where set_memory_decrypted() is called? Thanks, Tom > > > diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h > index 569272871375..f6c3638255d5 100644 > --- a/include/linux/swiotlb.h > +++ b/include/linux/swiotlb.h > @@ -73,6 +73,9 @@ extern enum swiotlb_force swiotlb_force; >   * @end:       The end address of the swiotlb memory pool. Used to do a > quick >   *             range check to see if the memory was in fact allocated by > this >   *             API. > + * @vaddr:     The vaddr of the swiotlb memory pool. The swiotlb memory pool > + *             may be remapped in the memory encrypted case and store > virtual > + *             address for bounce buffer operation. >   * @nslabs:    The number of IO TLB blocks (in groups of 64) between > @start and >   *             @end. For default swiotlb, this is command line > adjustable via >   *             setup_io_tlb_npages. > @@ -92,6 +95,7 @@ extern enum swiotlb_force swiotlb_force; >  struct io_tlb_mem { >         phys_addr_t start; >         phys_addr_t end; > +       void *vaddr; >         unsigned long nslabs; >         unsigned long used; >         unsigned int index; > @@ -186,4 +190,6 @@ static inline bool is_swiotlb_for_alloc(struct device > *dev) >  } >  #endif /* CONFIG_DMA_RESTRICTED_POOL */ > > +extern phys_addr_t swiotlb_unencrypted_base; > + >  #endif /* __LINUX_SWIOTLB_H */ > diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c > index 8e840fbbed7c..34e6ade4f73c 100644 > --- a/kernel/dma/swiotlb.c > +++ b/kernel/dma/swiotlb.c > @@ -50,6 +50,7 @@ >  #include >  #include > > +#include >  #include >  #include >  #include > @@ -72,6 +73,8 @@ enum swiotlb_force swiotlb_force; > >  struct io_tlb_mem io_tlb_default_mem; > > +phys_addr_t swiotlb_unencrypted_base; > + >  /* >   * Max segment that we can provide which (if pages are contingous) will >   * not be bounced (unless SWIOTLB_FORCE is set). > @@ -155,6 +158,27 @@ static inline unsigned long nr_slots(u64 val) >         return DIV_ROUND_UP(val, IO_TLB_SIZE); >  } > > +/* > + * Remap swioltb memory in the unencrypted physical address space > + * when swiotlb_unencrypted_base is set. (e.g. for Hyper-V AMD SEV-SNP > + * Isolation VMs). > + */ > +void *swiotlb_mem_remap(struct io_tlb_mem *mem, unsigned long bytes) > +{ > +       void *vaddr = NULL; > + > +       if (swiotlb_unencrypted_base) { > +               phys_addr_t paddr = mem->start + swiotlb_unencrypted_base; > + > +               vaddr = memremap(paddr, bytes, MEMREMAP_WB); > +               if (!vaddr) > +                       pr_err("Failed to map the unencrypted memory %llx > size %lx.\n", > +                              paddr, bytes); > +       } > + > +       return vaddr; > +} > + >  /* >   * Early SWIOTLB allocation may be too early to allow an architecture to >   * perform the desired operations.  This function allows the > architecture to > @@ -172,7 +196,12 @@ void __init swiotlb_update_mem_attributes(void) >         vaddr = phys_to_virt(mem->start); >         bytes = PAGE_ALIGN(mem->nslabs << IO_TLB_SHIFT); >         set_memory_decrypted((unsigned long)vaddr, bytes >> PAGE_SHIFT); > -       memset(vaddr, 0, bytes); > + > +       mem->vaddr = swiotlb_mem_remap(mem, bytes); > +       if (!mem->vaddr) > +               mem->vaddr = vaddr; > + > +       memset(mem->vaddr, 0, bytes); >  } > >  static void swiotlb_init_io_tlb_mem(struct io_tlb_mem *mem, phys_addr_t > start, > @@ -196,7 +225,17 @@ static void swiotlb_init_io_tlb_mem(struct io_tlb_mem > *mem, phys_addr_t start, >                 mem->slots[i].orig_addr = INVALID_PHYS_ADDR; >                 mem->slots[i].alloc_size = 0; >         } > + > +       /* > +        * If swiotlb_unencrypted_base is set, the bounce buffer memory will > +        * be remapped and cleared in swiotlb_update_mem_attributes. > +        */ > +       if (swiotlb_unencrypted_base) > +               return; > + >         memset(vaddr, 0, bytes); > +       mem->vaddr = vaddr; > +       return; >  } > >  int __init swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int > verbose) > @@ -371,7 +410,7 @@ static void swiotlb_bounce(struct device *dev, > phys_addr_t tlb_addr, size_t size >         phys_addr_t orig_addr = mem->slots[index].orig_addr; >         size_t alloc_size = mem->slots[index].alloc_size; >         unsigned long pfn = PFN_DOWN(orig_addr); > -       unsigned char *vaddr = phys_to_virt(tlb_addr); > +       unsigned char *vaddr = mem->vaddr + tlb_addr - mem->start; >         unsigned int tlb_offset, orig_addr_offset; > >         if (orig_addr == INVALID_PHYS_ADDR) > > > Thanks. >