lkml.org 
[lkml]   [2020]   [Feb]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    SubjectRE: [PATCH AUTOSEL 5.5 389/542] clocksource/drivers/hyper-v: Reserve PAGE_SIZE space for tsc page
    Date
    This patch does not need to be backported to any stable releases.  It is prep work for guests on Hyper-V ARM64 when the guest page size is 16K or 64K, and that functionality isn't upstream yet.

    Michael

    > -----Original Message-----
    > From: Sasha Levin <sashal@kernel.org>
    > Sent: Friday, February 14, 2020 7:46 AM
    > To: linux-kernel@vger.kernel.org; stable@vger.kernel.org
    > Cc: Boqun Feng <boqun.feng@gmail.com>; linux-hyperv@vger.kernel.org; Michael Kelley
    > <mikelley@microsoft.com>; Daniel Lezcano <daniel.lezcano@linaro.org>; Sasha Levin
    > <sashal@kernel.org>
    > Subject: [PATCH AUTOSEL 5.5 389/542] clocksource/drivers/hyper-v: Reserve PAGE_SIZE
    > space for tsc page
    >
    > From: Boqun Feng <boqun.feng@gmail.com>
    >
    > [ Upstream commit ddc61bbc45017726a2b450350d476b4dc5ae25ce ]
    >
    > Currently, the reserved size for a tsc page is 4K, which is enough for
    > communicating with hypervisor. However, in the case where we want to
    > export the tsc page to userspace (e.g. for vDSO to read the
    > clocksource), the tsc page should be at least PAGE_SIZE, otherwise, when
    > PAGE_SIZE is larger than 4K, extra kernel data will be mapped into
    > userspace, which means leaking kernel information.
    >
    > Therefore reserve PAGE_SIZE space for tsc_pg as a preparation for the
    > vDSO support of ARM64 in the future. Also, while at it, replace all
    > reference to tsc_pg with hv_get_tsc_page() since it should be the only
    > interface to access tsc page.
    >
    > Signed-off-by: Boqun Feng (Microsoft) <boqun.feng@gmail.com>
    > Cc: linux-hyperv@vger.kernel.org
    > Reviewed-by: Michael Kelley <mikelley@microsoft.com>
    > Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
    > Link:
    > https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.kernel.org%2Fr
    > %2F20191126021723.4710-1-
    > boqun.feng%40gmail.com&amp;data=02%7C01%7Cmikelley%40microsoft.com%7C2f481a9
    > 3db624cb4b5e208d7b16691f6%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C6371
    > 72926408924092&amp;sdata=%2F1JNMBiq7l1ufSsWphZb%2FMLNep2EIOCzlXcG%2F9foZNw
    > %3D&amp;reserved=0
    > Signed-off-by: Sasha Levin <sashal@kernel.org>
    > ---
    > drivers/clocksource/hyperv_timer.c | 11 +++++++----
    > 1 file changed, 7 insertions(+), 4 deletions(-)
    >
    > diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
    > index 287d8d58c21ac..b6ea3a2093c56 100644
    > --- a/drivers/clocksource/hyperv_timer.c
    > +++ b/drivers/clocksource/hyperv_timer.c
    > @@ -307,17 +307,20 @@ EXPORT_SYMBOL_GPL(hv_stimer_global_cleanup);
    > struct clocksource *hyperv_cs;
    > EXPORT_SYMBOL_GPL(hyperv_cs);
    >
    > -static struct ms_hyperv_tsc_page tsc_pg __aligned(PAGE_SIZE);
    > +static union {
    > + struct ms_hyperv_tsc_page page;
    > + u8 reserved[PAGE_SIZE];
    > +} tsc_pg __aligned(PAGE_SIZE);
    >
    > struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
    > {
    > - return &tsc_pg;
    > + return &tsc_pg.page;
    > }
    > EXPORT_SYMBOL_GPL(hv_get_tsc_page);
    >
    > static u64 notrace read_hv_clock_tsc(struct clocksource *arg)
    > {
    > - u64 current_tick = hv_read_tsc_page(&tsc_pg);
    > + u64 current_tick = hv_read_tsc_page(hv_get_tsc_page());
    >
    > if (current_tick == U64_MAX)
    > hv_get_time_ref_count(current_tick);
    > @@ -372,7 +375,7 @@ static bool __init hv_init_tsc_clocksource(void)
    > return false;
    >
    > hyperv_cs = &hyperv_cs_tsc;
    > - phys_addr = virt_to_phys(&tsc_pg);
    > + phys_addr = virt_to_phys(hv_get_tsc_page());
    >
    > /*
    > * The Hyper-V TLFS specifies to preserve the value of reserved
    > --
    > 2.20.1

    \
     
     \ /
      Last update: 2020-02-14 18:19    [W:2.412 / U:1.160 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site