Hi Kazu,
On Thu, Dec 5, 2019 at 9:00 PM Kazuhito Hagio <k-ha...@ab.jp.nec.com> wrote:
>
> > -----Original Message-----
> > > -----Original Message-----
> > > With ARMv8.2-LVA architecture extension availability, arm64 hardware
> > > which supports this extension can support upto 52-bit virtual
> > > addresses. It is specially useful for having a 52-bit user-space virtual
> > > address space while the kernel can still retain 48-bit/52-bit virtual
> > > addressing.
> > >
> > > Since at the moment we enable the support of this extension in the
> > > kernel via a CONFIG flag (CONFIG_ARM64_VA_BITS_52), so there are
> > > no clear mechanisms in user-space to determine this CONFIG
> > > flag value and use it to determine the kernel-space VA address range
> > > values.
> > >
> > > 'makedumpfile' can instead use 'TCR_EL1.T1SZ' value from vmcoreinfo
> > > which indicates the size offset of the memory region addressed by
> > > TTBR1_EL1 (and hence can be used for determining the
> > > vabits_actual value).
> > >
> > > The user-space computation for determining whether an address lies in
> > > the linear map range is the same as we have in kernel-space:
> > >
> > > #define __is_lm_address(addr) (!(((u64)addr) & BIT(vabits_actual -
> > > 1)))
> > >
> > > I have sent a kernel patch upstream to add 'TCR_EL1.T1SZ' to
> > > vmcoreinfo for arm64 (see [0]).
> > >
> > > This patch is in accordance with ARMv8 Architecture Reference Manual
> > > version D.a
> > >
> > > Note that with these changes the '--mem-usage' option will not work
> > > properly for arm64 (a subsequent patch in this series will address the
> > > same) and there is a discussion on-going with the arm64 maintainers to
> > > find a way-out for the same (via standard kernel symbols like _stext).
> > >
> > > [0].http://lists.infradead.org/pipermail/kexec/2019-November/023962.html
> > >
> > > Cc: Kazuhito Hagio <k-ha...@ab.jp.nec.com>
> > > Cc: John Donnelly <john.p.donne...@oracle.com>
> > > Cc: kexec@lists.infradead.org
> > > Signed-off-by: Bhupesh Sharma <bhsha...@redhat.com>
> > > ---
> > > arch/arm64.c | 148
> > > +++++++++++++++++++++++++++++++++++++++++++++------------
> > > makedumpfile.c | 2 +
> > > makedumpfile.h | 3 +-
> > > 3 files changed, 122 insertions(+), 31 deletions(-)
> > >
> > > diff --git a/arch/arm64.c b/arch/arm64.c
> > > index ecb19139e178..094d73b8a60f 100644
> > > --- a/arch/arm64.c
> > > +++ b/arch/arm64.c
> > > @@ -47,6 +47,7 @@ typedef struct {
> > > static int lpa_52_bit_support_available;
> > > static int pgtable_level;
> > > static int va_bits;
> > > +static int vabits_actual;
> > > static unsigned long kimage_voffset;
> > >
> > > #define SZ_4K 4096
> > > @@ -218,12 +219,19 @@ pmd_page_paddr(pmd_t pmd)
> > > #define pte_index(vaddr) (((vaddr) >> PAGESHIFT()) &
> > > (PTRS_PER_PTE - 1))
> > > #define pte_offset(dir, vaddr) (pmd_page_paddr((*dir)) +
> > > pte_index(vaddr) * sizeof(pte_t))
> > >
> > > +/*
> > > + * The linear kernel range starts at the bottom of the virtual address
> > > + * space. Testing the top bit for the start of the region is a
> > > + * sufficient check and avoids having to worry about the tag.
> > > + */
> > > +#define is_linear_addr(addr) (!(((unsigned long)addr) & (1UL <<
> > > (vabits_actual - 1))))
> >
> > Does this check cover 5.3 or earlier kernels?
> > There is no case that vabits_actual is zero?
We can set vabits_actual as va_bits for older kernels. That shouldn't
be a big change.
Will add it in v5. See more below ...
> As you know, 14c127c957c1 ("arm64: mm: Flip kernel VA space") changed
> the check for linear address:
>
> -#define __is_lm_address(addr) (!!((addr) & BIT(VA_BITS - 1)))
> +#define __is_lm_address(addr) (!((addr) & BIT(VA_BITS - 1)))
>
> so if we use the same check as kernel has, I think we will need the
> former one to support earlier kernels.
See above, we can use va_bits where vabits_actual is not present.
> > > +
> > > static unsigned long long
> > > __pa(unsigned long vaddr)
> > > {
> > > if (kimage_voffset == NOT_FOUND_NUMBER ||
> > > - (vaddr >= PAGE_OFFSET))
> > > - return (vaddr - PAGE_OFFSET + info->phys_base);
> > > + is_linear_addr(vaddr))
> > > + return (vaddr + info->phys_base - PAGE_OFFSET);
> > > else
> > > return (vaddr - kimage_voffset);
> > > }
> > > @@ -253,6 +261,7 @@ static int calculate_plat_config(void)
> > > (PAGESIZE() == SZ_64K && va_bits == 42)) {
> > > pgtable_level = 2;
> > > } else if ((PAGESIZE() == SZ_64K && va_bits == 48) ||
> > > + (PAGESIZE() == SZ_64K && va_bits == 52) ||
> > > (PAGESIZE() == SZ_4K && va_bits == 39) ||
> > > (PAGESIZE() == SZ_16K && va_bits == 47)) {
> > > pgtable_level = 3;
> > > @@ -287,6 +296,16 @@ get_phys_base_arm64(void)
> > > return TRUE;
> > > }
> > >
> > > + /* If both vabits_actual and va_bits are now initialized, always
> > > + * prefer vabits_actual over va_bits to calculate PAGE_OFFSET
> > > + * value.
> > > + */
> > > + if (vabits_actual && va_bits && vabits_actual != va_bits) {
> > > + info->page_offset = (-(1UL << vabits_actual));
> > > + DEBUG_MSG("page_offset : %lx (via vabits_actual)\n",
> > > + info->page_offset);
> > > + }
> > > +
> >
> > Is this for --mem-usage?
> > If so, let's drop from this patch and think about it later because
> > some additional base functions will be needed for the option, I think.
Ok.
> > > if (get_num_pt_loads() && PAGE_OFFSET) {
> > > for (i = 0;
> > > get_pt_load(i, &phys_start, NULL, &virt_start, NULL);
> > > @@ -406,6 +425,73 @@ get_stext_symbol(void)
> > > return(found ? kallsym : FALSE);
> > > }
> > >
> > > +static int
> > > +get_va_bits_from_stext_arm64(void)
> > > +{
> > > + ulong _stext;
> > > +
> > > + _stext = get_stext_symbol();
> > > + if (!_stext) {
> > > + ERRMSG("Can't get the symbol of _stext.\n");
> > > + return FALSE;
> > > + }
> > > +
> > > + /* Derive va_bits as per arch/arm64/Kconfig. Note that this is a
> > > + * best case approximation at the moment, as there can be
> > > + * inconsistencies in this calculation (for e.g., for
> > > + * 52-bit kernel VA case, even the 48th bit might be set in
> > > + * the _stext symbol).
> > > + *
> > > + * So, we need to rely on the actual VA_BITS symbol in the
> > > + * vmcoreinfo for a accurate value.
> > > + *
> > > + * TODO: Improve this further once there is a closure with arm64
> > > + * kernel maintainers on the same.
> > > + */
> > > + if ((_stext & PAGE_OFFSET_52) == PAGE_OFFSET_52) {
> > > + va_bits = 52;
> > > + } else if ((_stext & PAGE_OFFSET_48) == PAGE_OFFSET_48) {
> > > + va_bits = 48;
> > > + } else if ((_stext & PAGE_OFFSET_47) == PAGE_OFFSET_47) {
> > > + va_bits = 47;
> > > + } else if ((_stext & PAGE_OFFSET_42) == PAGE_OFFSET_42) {
> > > + va_bits = 42;
> > > + } else if ((_stext & PAGE_OFFSET_39) == PAGE_OFFSET_39) {
> > > + va_bits = 39;
> > > + } else if ((_stext & PAGE_OFFSET_36) == PAGE_OFFSET_36) {
> > > + va_bits = 36;
> > > + } else {
> > > + ERRMSG("Cannot find a proper _stext for calculating
> > > VA_BITS\n");
> > > + return FALSE;
> > > + }
> > > +
> > > + DEBUG_MSG("va_bits : %d (_stext) (approximation)\n", va_bits);
> > > +
> > > + return TRUE;
> > > +}
> > > +
> > > +static void
> > > +get_page_offset_arm64(void)
> > > +{
> > > + /* Check if 'vabits_actual' is initialized yet.
> > > + * If not, our best bet is to use 'va_bits' to calculate
> > > + * the PAGE_OFFSET value, otherwise use 'vabits_actual'
> > > + * for the same.
> > > + *
> > > + * See arch/arm64/include/asm/memory.h for more details.
> > > + */
> > > + if (!vabits_actual) {
> > > + info->page_offset = (-(1UL << va_bits));
> > > + DEBUG_MSG("page_offset : %lx (approximation)\n",
> > > + info->page_offset);
> > > + } else {
> > > + info->page_offset = (-(1UL << vabits_actual));
> > > + DEBUG_MSG("page_offset : %lx (accurate)\n",
> > > + info->page_offset);
> > > + }
> >
> > Does this support 5.3 or earlier kernels?
>
> Because I didn't see the old page_offset calculation below in this patch:
>
> > > - info->page_offset = (0xffffffffffffffffUL) << (va_bits - 1);
>
> I was thinking that if there is a NUMBER(tcr_el1_t1sz) in vmcoreinfo,
> we assume the kernel has the 'flipped' VA space. And if there is no
> NUMBER(tcr_el1_t1sz), then older 'non-flipped' VA [1].
Yes vabits_actual will be not found in such a case and we can use
va_bits in such a case and similarly helper routines for page table
walk/page_offset calculation may need modification.
Will fix in v5.
> This might be a bit fragile against backport, but it requires less
> vmcoreinfo, and older kernels don't need NUMBER(tcr_el1_t1sz).
> (they might need NUMBER(MAX_USER_VA_BITS) like RHEL8 though.)
I think since this is an upstream fix, we should look at a generic fix
(not restricted to RHEL, which anyway can contain out of tree fixes).
I will send a v5 shortly with the suggested fixes.
Regards,
Bhupesh
> What do you think?
>
> [1]
> https://github.com/k-hagio/makedumpfile/commit/fd9d86ea05b38e9edbb8c0ac3ebd612d5d485df3#diff-73f1cf659e8099a2f3a94f38063f97ecR400
>
> Thanks,
> Kazu
>
>
> >
> > Thanks,
> > Kazu
> >
> > > +
> > > +}
> > > +
> > > int
> > > get_machdep_info_arm64(void)
> > > {
> > > @@ -420,8 +506,33 @@ get_machdep_info_arm64(void)
> > > /* Check if va_bits is still not initialized. If still 0, call
> > > * get_versiondep_info() to initialize the same.
> > > */
> > > + if (NUMBER(VA_BITS) != NOT_FOUND_NUMBER) {
> > > + va_bits = NUMBER(VA_BITS);
> > > + DEBUG_MSG("va_bits : %d (vmcoreinfo)\n",
> > > + va_bits);
> > > + }
> > > +
> > > + /* Check if va_bits is still not initialized. If still 0, call
> > > + * get_versiondep_info() to initialize the same from _stext
> > > + * symbol.
> > > + */
> > > if (!va_bits)
> > > - get_versiondep_info_arm64();
> > > + if (get_va_bits_from_stext_arm64() == FALSE)
> > > + return FALSE;
> > > +
> > > + get_page_offset_arm64();
> > > +
> > > + /* See TCR_EL1, Translation Control Register (EL1) register
> > > + * description in the ARMv8 Architecture Reference Manual.
> > > + * Basically, we can use the TCR_EL1.T1SZ
> > > + * value to determine the virtual addressing range supported
> > > + * in the kernel-space (i.e. vabits_actual).
> > > + */
> > > + if (NUMBER(tcr_el1_t1sz) != NOT_FOUND_NUMBER) {
> > > + vabits_actual = 64 - NUMBER(tcr_el1_t1sz);
> > > + DEBUG_MSG("vabits_actual : %d (vmcoreinfo)\n",
> > > + vabits_actual);
> > > + }
> > >
> > > if (!calculate_plat_config()) {
> > > ERRMSG("Can't determine platform config values\n");
> > > @@ -459,34 +570,11 @@ get_xen_info_arm64(void)
> > > int
> > > get_versiondep_info_arm64(void)
> > > {
> > > - ulong _stext;
> > > -
> > > - _stext = get_stext_symbol();
> > > - if (!_stext) {
> > > - ERRMSG("Can't get the symbol of _stext.\n");
> > > - return FALSE;
> > > - }
> > > -
> > > - /* Derive va_bits as per arch/arm64/Kconfig */
> > > - if ((_stext & PAGE_OFFSET_36) == PAGE_OFFSET_36) {
> > > - va_bits = 36;
> > > - } else if ((_stext & PAGE_OFFSET_39) == PAGE_OFFSET_39) {
> > > - va_bits = 39;
> > > - } else if ((_stext & PAGE_OFFSET_42) == PAGE_OFFSET_42) {
> > > - va_bits = 42;
> > > - } else if ((_stext & PAGE_OFFSET_47) == PAGE_OFFSET_47) {
> > > - va_bits = 47;
> > > - } else if ((_stext & PAGE_OFFSET_48) == PAGE_OFFSET_48) {
> > > - va_bits = 48;
> > > - } else {
> > > - ERRMSG("Cannot find a proper _stext for calculating
> > > VA_BITS\n");
> > > - return FALSE;
> > > - }
> > > -
> > > - info->page_offset = (0xffffffffffffffffUL) << (va_bits - 1);
> > > + if (!va_bits)
> > > + if (get_va_bits_from_stext_arm64() == FALSE)
> > > + return FALSE;
> > >
> > > - DEBUG_MSG("va_bits : %d\n", va_bits);
> > > - DEBUG_MSG("page_offset : %lx\n", info->page_offset);
> > > + get_page_offset_arm64();
> > >
> > > return TRUE;
> > > }
> > > diff --git a/makedumpfile.c b/makedumpfile.c
> > > index 4a000112ba59..baf559e4d74e 100644
> > > --- a/makedumpfile.c
> > > +++ b/makedumpfile.c
> > > @@ -2314,6 +2314,7 @@ write_vmcoreinfo_data(void)
> > > WRITE_NUMBER("HUGETLB_PAGE_DTOR", HUGETLB_PAGE_DTOR);
> > > #ifdef __aarch64__
> > > WRITE_NUMBER("VA_BITS", VA_BITS);
> > > + WRITE_NUMBER_UNSIGNED("tcr_el1_t1sz", tcr_el1_t1sz);
> > > WRITE_NUMBER_UNSIGNED("PHYS_OFFSET", PHYS_OFFSET);
> > > WRITE_NUMBER_UNSIGNED("kimage_voffset", kimage_voffset);
> > > #endif
> > > @@ -2720,6 +2721,7 @@ read_vmcoreinfo(void)
> > > READ_NUMBER("KERNEL_IMAGE_SIZE", KERNEL_IMAGE_SIZE);
> > > #ifdef __aarch64__
> > > READ_NUMBER("VA_BITS", VA_BITS);
> > > + READ_NUMBER_UNSIGNED("tcr_el1_t1sz", tcr_el1_t1sz);
> > > READ_NUMBER_UNSIGNED("PHYS_OFFSET", PHYS_OFFSET);
> > > READ_NUMBER_UNSIGNED("kimage_voffset", kimage_voffset);
> > > #endif
> > > diff --git a/makedumpfile.h b/makedumpfile.h
> > > index ac11e906b5b7..7eab6507c8df 100644
> > > --- a/makedumpfile.h
> > > +++ b/makedumpfile.h
> > > @@ -974,7 +974,7 @@ int get_versiondep_info_arm64(void);
> > > int get_xen_basic_info_arm64(void);
> > > int get_xen_info_arm64(void);
> > > unsigned long get_kaslr_offset_arm64(unsigned long vaddr);
> > > -#define paddr_to_vaddr_arm64(X) (((X) - info->phys_base) | PAGE_OFFSET)
> > > +#define paddr_to_vaddr_arm64(X) (((X) - (info->phys_base - PAGE_OFFSET)))
> > >
> > > #define find_vmemmap() stub_false()
> > > #define vaddr_to_paddr(X) vaddr_to_paddr_arm64(X)
> > > @@ -1937,6 +1937,7 @@ struct number_table {
> > > long KERNEL_IMAGE_SIZE;
> > > #ifdef __aarch64__
> > > long VA_BITS;
> > > + unsigned long tcr_el1_t1sz;
> > > unsigned long PHYS_OFFSET;
> > > unsigned long kimage_voffset;
> > > #endif
> > > --
> > > 2.7.4
> > >
>
>
>
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