[PATCH v2] pnv/xive2: Fix TIMA offset for indirect access

[PATCH v2] pnv/xive2: Fix TIMA offset for indirect access

[Frederic Barrat]

Direct TIMA operations can be done through 4 pages, each with a
different privilege level dictating what fields can be accessed. On
the other hand, indirect TIMA accesses on P10 are done through a
single page, which is the equivalent of the most privileged page of
direct TIMA accesses.

The offset in the IC bar of an indirect access specifies what hw
thread is targeted (page shift bits) and the offset in the
TIMA being accessed (the page offset bits). When the indirect
access is calling the underlying direct access functions, it is
therefore important to clearly separate the 2, as the direct functions
assume any page shift bits define the privilege ring level. For
indirect accesses, those bits must be 0. This patch fixes the offset
passed to direct TIMA functions.

It didn't matter for SMT1, as the 2 least significant bits of the page
shift are part of the hw thread ID and always 0, so the direct TIMA
functions were accessing the privilege ring 0 page. With SMT4/8, it is
no longer true.

The fix is specific to P10, as indirect TIMA access on P9 was handled
differently.

Signed-off-by: Frederic Barrat <fbarrat@linux.ibm.com>
---
Changelog:
v2: rename function and variable
    rebase to Danel's ppc-next

hw/intc/pnv_xive2.c | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/hw/intc/pnv_xive2.c b/hw/intc/pnv_xive2.c
index e8ab176de6..82fcd3ea22 100644
--- a/hw/intc/pnv_xive2.c
+++ b/hw/intc/pnv_xive2.c
@@ -1590,6 +1590,18 @@ static uint32_t pnv_xive2_ic_tm_get_pir(PnvXive2 *xive, hwaddr offset)
     return xive->chip->chip_id << 8 | offset >> xive->ic_shift;
 }
 
+static uint32_t pnv_xive2_ic_tm_get_hw_page_offset(PnvXive2 *xive,
+                                                   hwaddr offset)
+{
+    /*
+     * Indirect TIMA accesses are similar to direct accesses for
+     * privilege ring 0. So remove any traces of the hw thread ID from
+     * the offset in the IC BAR as it could be interpreted as the ring
+     * privilege when calling the underlying direct access functions.
+     */
+    return offset & ((1ull << xive->ic_shift) - 1);
+}
+
 static XiveTCTX *pnv_xive2_get_indirect_tctx(PnvXive2 *xive, uint32_t pir)
 {
     PnvChip *chip = xive->chip;
@@ -1612,14 +1624,16 @@ static uint64_t pnv_xive2_ic_tm_indirect_read(void *opaque, hwaddr offset,
                                               unsigned size)
 {
     PnvXive2 *xive = PNV_XIVE2(opaque);
+    hwaddr hw_page_offset;
     uint32_t pir;
     XiveTCTX *tctx;
     uint64_t val = -1;
 
     pir = pnv_xive2_ic_tm_get_pir(xive, offset);
+    hw_page_offset = pnv_xive2_ic_tm_get_hw_page_offset(xive, offset);
     tctx = pnv_xive2_get_indirect_tctx(xive, pir);
     if (tctx) {
-        val = xive_tctx_tm_read(NULL, tctx, offset, size);
+        val = xive_tctx_tm_read(NULL, tctx, hw_page_offset, size);
     }
 
     return val;
@@ -1629,13 +1643,15 @@ static void pnv_xive2_ic_tm_indirect_write(void *opaque, hwaddr offset,
                                            uint64_t val, unsigned size)
 {
     PnvXive2 *xive = PNV_XIVE2(opaque);
+    hwaddr hw_page_offset;
     uint32_t pir;
     XiveTCTX *tctx;
 
     pir = pnv_xive2_ic_tm_get_pir(xive, offset);
+    hw_page_offset = pnv_xive2_ic_tm_get_hw_page_offset(xive, offset);
     tctx = pnv_xive2_get_indirect_tctx(xive, pir);
     if (tctx) {
-        xive_tctx_tm_write(NULL, tctx, offset, val, size);
+        xive_tctx_tm_write(NULL, tctx, hw_page_offset, val, size);
     }
 }
 
-- 
2.41.0

Re: [PATCH v2] pnv/xive2: Fix TIMA offset for indirect access

[Cédric Le Goater]

On 7/3/23 10:08, Frederic Barrat wrote:
> Direct TIMA operations can be done through 4 pages, each with a
> different privilege level dictating what fields can be accessed. On
> the other hand, indirect TIMA accesses on P10 are done through a
> single page, which is the equivalent of the most privileged page of
> direct TIMA accesses.
> 
> The offset in the IC bar of an indirect access specifies what hw
> thread is targeted (page shift bits) and the offset in the
> TIMA being accessed (the page offset bits). When the indirect
> access is calling the underlying direct access functions, it is
> therefore important to clearly separate the 2, as the direct functions
> assume any page shift bits define the privilege ring level. For
> indirect accesses, those bits must be 0. This patch fixes the offset
> passed to direct TIMA functions.
> 
> It didn't matter for SMT1, as the 2 least significant bits of the page
> shift are part of the hw thread ID and always 0, so the direct TIMA
> functions were accessing the privilege ring 0 page. With SMT4/8, it is
> no longer true.
> 
> The fix is specific to P10, as indirect TIMA access on P9 was handled
> differently.
> 
> Signed-off-by: Frederic Barrat <fbarrat@linux.ibm.com>


Reviewed-by: Cédric Le Goater <clg@kaod.org>

Thanks,

C.


> ---
> Changelog:
> v2: rename function and variable
>      rebase to Danel's ppc-next
> 
> hw/intc/pnv_xive2.c | 20 ++++++++++++++++++--
>   1 file changed, 18 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/intc/pnv_xive2.c b/hw/intc/pnv_xive2.c
> index e8ab176de6..82fcd3ea22 100644
> --- a/hw/intc/pnv_xive2.c
> +++ b/hw/intc/pnv_xive2.c
> @@ -1590,6 +1590,18 @@ static uint32_t pnv_xive2_ic_tm_get_pir(PnvXive2 *xive, hwaddr offset)
>       return xive->chip->chip_id << 8 | offset >> xive->ic_shift;
>   }
>   
> +static uint32_t pnv_xive2_ic_tm_get_hw_page_offset(PnvXive2 *xive,
> +                                                   hwaddr offset)
> +{
> +    /*
> +     * Indirect TIMA accesses are similar to direct accesses for
> +     * privilege ring 0. So remove any traces of the hw thread ID from
> +     * the offset in the IC BAR as it could be interpreted as the ring
> +     * privilege when calling the underlying direct access functions.
> +     */
> +    return offset & ((1ull << xive->ic_shift) - 1);
> +}
> +
>   static XiveTCTX *pnv_xive2_get_indirect_tctx(PnvXive2 *xive, uint32_t pir)
>   {
>       PnvChip *chip = xive->chip;
> @@ -1612,14 +1624,16 @@ static uint64_t pnv_xive2_ic_tm_indirect_read(void *opaque, hwaddr offset,
>                                                 unsigned size)
>   {
>       PnvXive2 *xive = PNV_XIVE2(opaque);
> +    hwaddr hw_page_offset;
>       uint32_t pir;
>       XiveTCTX *tctx;
>       uint64_t val = -1;
>   
>       pir = pnv_xive2_ic_tm_get_pir(xive, offset);
> +    hw_page_offset = pnv_xive2_ic_tm_get_hw_page_offset(xive, offset);
>       tctx = pnv_xive2_get_indirect_tctx(xive, pir);
>       if (tctx) {
> -        val = xive_tctx_tm_read(NULL, tctx, offset, size);
> +        val = xive_tctx_tm_read(NULL, tctx, hw_page_offset, size);
>       }
>   
>       return val;
> @@ -1629,13 +1643,15 @@ static void pnv_xive2_ic_tm_indirect_write(void *opaque, hwaddr offset,
>                                              uint64_t val, unsigned size)
>   {
>       PnvXive2 *xive = PNV_XIVE2(opaque);
> +    hwaddr hw_page_offset;
>       uint32_t pir;
>       XiveTCTX *tctx;
>   
>       pir = pnv_xive2_ic_tm_get_pir(xive, offset);
> +    hw_page_offset = pnv_xive2_ic_tm_get_hw_page_offset(xive, offset);
>       tctx = pnv_xive2_get_indirect_tctx(xive, pir);
>       if (tctx) {
> -        xive_tctx_tm_write(NULL, tctx, offset, val, size);
> +        xive_tctx_tm_write(NULL, tctx, hw_page_offset, val, size);
>       }
>   }
>   

Re: [PATCH v2] pnv/xive2: Fix TIMA offset for indirect access

[Daniel Henrique Barboza]

On 7/3/23 05:08, Frederic Barrat wrote:
> Direct TIMA operations can be done through 4 pages, each with a
> different privilege level dictating what fields can be accessed. On
> the other hand, indirect TIMA accesses on P10 are done through a
> single page, which is the equivalent of the most privileged page of
> direct TIMA accesses.
> 
> The offset in the IC bar of an indirect access specifies what hw
> thread is targeted (page shift bits) and the offset in the
> TIMA being accessed (the page offset bits). When the indirect
> access is calling the underlying direct access functions, it is
> therefore important to clearly separate the 2, as the direct functions
> assume any page shift bits define the privilege ring level. For
> indirect accesses, those bits must be 0. This patch fixes the offset
> passed to direct TIMA functions.
> 
> It didn't matter for SMT1, as the 2 least significant bits of the page
> shift are part of the hw thread ID and always 0, so the direct TIMA
> functions were accessing the privilege ring 0 page. With SMT4/8, it is
> no longer true.
> 
> The fix is specific to P10, as indirect TIMA access on P9 was handled
> differently.
> 
> Signed-off-by: Frederic Barrat <fbarrat@linux.ibm.com>
> ---

Queued in gitlab.com/danielhb/qemu/tree/ppc-next. Thanks,


Daniel

> Changelog:
> v2: rename function and variable
>      rebase to Danel's ppc-next
> 
> hw/intc/pnv_xive2.c | 20 ++++++++++++++++++--
>   1 file changed, 18 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/intc/pnv_xive2.c b/hw/intc/pnv_xive2.c
> index e8ab176de6..82fcd3ea22 100644
> --- a/hw/intc/pnv_xive2.c
> +++ b/hw/intc/pnv_xive2.c
> @@ -1590,6 +1590,18 @@ static uint32_t pnv_xive2_ic_tm_get_pir(PnvXive2 *xive, hwaddr offset)
>       return xive->chip->chip_id << 8 | offset >> xive->ic_shift;
>   }
>   
> +static uint32_t pnv_xive2_ic_tm_get_hw_page_offset(PnvXive2 *xive,
> +                                                   hwaddr offset)
> +{
> +    /*
> +     * Indirect TIMA accesses are similar to direct accesses for
> +     * privilege ring 0. So remove any traces of the hw thread ID from
> +     * the offset in the IC BAR as it could be interpreted as the ring
> +     * privilege when calling the underlying direct access functions.
> +     */
> +    return offset & ((1ull << xive->ic_shift) - 1);
> +}
> +
>   static XiveTCTX *pnv_xive2_get_indirect_tctx(PnvXive2 *xive, uint32_t pir)
>   {
>       PnvChip *chip = xive->chip;
> @@ -1612,14 +1624,16 @@ static uint64_t pnv_xive2_ic_tm_indirect_read(void *opaque, hwaddr offset,
>                                                 unsigned size)
>   {
>       PnvXive2 *xive = PNV_XIVE2(opaque);
> +    hwaddr hw_page_offset;
>       uint32_t pir;
>       XiveTCTX *tctx;
>       uint64_t val = -1;
>   
>       pir = pnv_xive2_ic_tm_get_pir(xive, offset);
> +    hw_page_offset = pnv_xive2_ic_tm_get_hw_page_offset(xive, offset);
>       tctx = pnv_xive2_get_indirect_tctx(xive, pir);
>       if (tctx) {
> -        val = xive_tctx_tm_read(NULL, tctx, offset, size);
> +        val = xive_tctx_tm_read(NULL, tctx, hw_page_offset, size);
>       }
>   
>       return val;
> @@ -1629,13 +1643,15 @@ static void pnv_xive2_ic_tm_indirect_write(void *opaque, hwaddr offset,
>                                              uint64_t val, unsigned size)
>   {
>       PnvXive2 *xive = PNV_XIVE2(opaque);
> +    hwaddr hw_page_offset;
>       uint32_t pir;
>       XiveTCTX *tctx;
>   
>       pir = pnv_xive2_ic_tm_get_pir(xive, offset);
> +    hw_page_offset = pnv_xive2_ic_tm_get_hw_page_offset(xive, offset);
>       tctx = pnv_xive2_get_indirect_tctx(xive, pir);
>       if (tctx) {
> -        xive_tctx_tm_write(NULL, tctx, offset, val, size);
> +        xive_tctx_tm_write(NULL, tctx, hw_page_offset, val, size);
>       }
>   }
>